RESUMEN

Hyperactivity of hypothalamic-pituitary mediated hormone responses, such as to stimulation with a serotonin 1A (5-HT(1A)) receptor agonist, are a feature of depression which are normalized with clinical improvement during drug therapy. We previously reported that SSRIs induce desensitization of 5-HT(1A) receptor signaling in the paraventricular nucleus of the hypothalamus (PVN) while estradiol benzoate (EB) produces a more rapid, partial desensitization. In the current study, time course and dose-response experiments demonstrated that two once daily doses of EB is the minimum needed to induce the desensitization response as indicated by 5-HT(1A) receptor-stimulated release of oxytocin and that 10 µg/kg/day EB produces the maximal response, a partial desensitization of approximately 40%. The effects of two once daily injections of 10 µg/kg/day EB on Gαz and RGSZ1 proteins were examined as components of the 5-HT(1A) receptor signaling system, which mediates the release of oxytocin and adrenocorticotropic hormone. RGSZ1 appears to be a major target for EB-mediated responses in the 5-HT(1A) receptor signaling system. A 55 kD membrane-associate RGSZ1 protein was greatly increased in the PVN and rest of the hypothalamus and moderately increased in the dorsal hippocampus and amygdala after EB treatment as well as after an acute dose of a 5-HT(1A) receptor agonist. These results suggest that EB is a candidate for adjuvant therapy with SSRIs to hasten the therapeutic response and that RGSZ1 is a major target of EB therapy which could be explored as a target for novel therapeutic approaches for the treatment of depression.

Asunto(s)

Estradiol/análogos & derivados , Subunidades alfa de la Proteína de Unión al GTP/metabolismo , Proteínas Activadoras de GTPasa/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Receptor de Serotonina 5-HT1A/metabolismo , Transducción de Señal/efectos de los fármacos , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Animales , Relación Dosis-Respuesta a Droga , Estradiol/farmacología , Femenino , Oxitocina/sangre , Núcleo Hipotalámico Paraventricular/metabolismo , Proteínas RGS , Ratas , Ratas Sprague-Dawley , Agonistas de Receptores de Serotonina/farmacología

RESUMEN

Estrogen therapy used in combination with selective serotonin reuptake inhibitor (SSRI) treatment improves SSRI efficacy for the treatment of mood disorders. Desensitization of serotonin 1A (5-HT(1A)) receptors, which takes one to two weeks to develop in animals, is necessary for SSRI therapeutic efficacy. Estradiol modifies 5-HT(1A) receptor signaling and induces a partial desensitization in the paraventricular nucleus (PVN) of the rat within two days, but the mechanisms underlying this effect are currently unknown. The purpose of this study was to identify the estrogen receptor necessary for estradiol-induced 5-HT(1A) receptor desensitization. We previously showed that estrogen receptor ß is not necessary for 5-HT(1A) receptor desensitization and that selective activation of estrogen receptor GPR30 mimics the effects of estradiol in rat PVN. Here, we used a recombinant adenovirus containing GPR30 siRNAs to decrease GPR30 expression in the PVN. Reduction of GPR30 prevented estradiol-induced desensitization of 5-HT(1A) receptor as measured by hormonal responses to the selective 5-HT(1A) receptor agonist, (+)8-OH-DPAT. To determine the possible mechanisms underlying these effects, we investigated protein and mRNA levels of 5-HT(1A) receptor signaling components including 5-HT(1A) receptor, Gαz, and RGSz1. We found that two days of estradiol increased protein and mRNA expression of RGSz1, and decreased 5-HT(1A) receptor protein but increased 5-HT(1A) mRNA; GPR30 knockdown prevented the estradiol-induced changes in 5-HT(1A) receptor protein in the PVN. Taken together, these data demonstrate that GPR30 is necessary for estradiol-induced changes in the 5-HT(1A) receptor signaling pathway and desensitization of 5-HT(1A) receptor signaling.

Asunto(s)

Estradiol/farmacología , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Receptor de Serotonina 5-HT1A/metabolismo , Receptores Acoplados a Proteínas G/fisiología , Animales , Femenino , Expresión Génica/efectos de los fármacos , Células HEK293 , Humanos , Modelos Biológicos , Núcleo Hipotalámico Paraventricular/metabolismo , ARN Interferente Pequeño/farmacología , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT1A/genética , Receptor de Serotonina 5-HT1A/fisiología , Receptores Acoplados a Proteínas G/antagonistas & inhibidores , Receptores Acoplados a Proteínas G/genética , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética

RESUMEN

Chronic treatment with olanzapine causes desensitization of serotonin 2A receptor signaling. The purpose of the current study was to further understand the mechanisms underlying this desensitization response of serotonin 2A receptor signaling in vivo. We report that desensitization of serotonin 2A receptor stimulated-phospholipase C activity in rat frontal cortex induced by olanzapine is dependent on the activation of the JAK-STAT pathway. Olanzapine treatment for 7 days significantly increased the levels of the regulator of G protein signaling (RGS7) protein, RGS7 mRNA levels, and activation of JAK2 in rat frontal cortex. Pre-treatment with a JAK2 inhibitor AG490, significantly attenuated the olanzapine-induced reductions in serotonin 2A receptor-stimulated phospholipase C activity and prevented the olanzapine-induced increases in RGS7 mRNA and protein levels. In contrast, inhibition of the JAK-STAT pathway with AG490 did not reverse the olanzapine-induced desensitization of the serotonin 2A receptor pathway in the hypothalamic paraventricular nucleus mediating increases in plasma hormone levels. AG490 dose-dependently inhibited serotonin 2A receptor-stimulated oxytocin and corticosterone release. These results suggest that the olanzapine-induced increase in RGS7 expression is mediated by the activation of JAK-STAT and is necessary for olanzapine-induced desensitization of serotonin 2A receptor-stimulated phospholipase C activity in the frontal cortex but not serotonin 2A receptor-stimulated hormone release.

Asunto(s)

Antipsicóticos/farmacología , Benzodiazepinas/farmacología , Hormonas/metabolismo , Janus Quinasa 2/efectos de los fármacos , Corteza Prefrontal/efectos de los fármacos , Receptor de Serotonina 5-HT2A/efectos de los fármacos , Factor de Transcripción STAT3/efectos de los fármacos , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Transducción de Señal/efectos de los fármacos , Fosfolipasas de Tipo C/fisiología , Hormona Adrenocorticotrópica/sangre , Animales , Western Blotting , Corticosterona/sangre , Inhibidores Enzimáticos/farmacología , Janus Quinasa 2/antagonistas & inhibidores , Masculino , Olanzapina , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Fosforilación , Corteza Prefrontal/enzimología , Proteínas RGS/biosíntesis , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Ratas , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Transcripción STAT3/antagonistas & inhibidores , Tirfostinos/farmacología

RESUMEN

Selective serotonin reuptake inhibitors (SSRIs), such as Prozac, are used to treat mood disorders. SSRIs attenuate (i.e. desensitize) serotonin 1A (5-HT(1A)) receptor signaling, as demonstrated in rats through decreased release of oxytocin and adrenocorticotropin hormone (ACTH) following 5-HT(1A) receptor stimulation. Maximal therapeutic effects of SSRIs for treatment of mood disorders, as well as effects on hypothalamic 5-HT(1A) receptor signaling in animals, take 1 to 2 weeks to develop. Estradiol also attenuates 5-HT(1A) receptor signaling, but, in rats, these effects occur within 2 days; thus, estrogens or selective estrogen receptor modulators may serve as useful short-term tools to accelerate desensitization of 5-HT(1A) receptors in response to SSRIs if candidate estrogen receptor targets in the hypothalamus are identified. We found high levels of GPR30, which has been identified recently as a pertussis-toxin (PTX) sensitive G-protein-coupled estrogen receptor, in the hypothalamic paraventricular nucleus (PVN) of rats. Double-label immunohistochemistry revealed that GPR30 co-localizes with 5-HT(1A) receptors, corticotrophin releasing factor (CRF) and oxytocin in neurons in the PVN. Pretreatment with PTX to the PVN before peripheral injections of 17-beta-estradiol 3-benzoate completely prevented the reduction of the oxytocin response to the 5-HT(1A) receptor agonist, (+)-8-hydroxy-2-dipropylaminotetralin (DPAT). Treatment with the selective GRP30 agonist, G-1, attenuated 5-HT(1A) receptor signaling in the PVN as measured by an attenuated oxytocin (by 29%) and ACTH (by 31%) response to DPAT. This study indicates that a putative extra-nuclear estrogen receptor, GPR30, may play a role in estradiol-mediated attenuation of 5-HT(1A) receptor signaling, and potentially in accelerating the effects of SSRIs in treatment of mood disorders.

Asunto(s)

Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Serotonina/metabolismo , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Hormona Adrenocorticotrópica/sangre , Análisis de Varianza , Animales , Benzoatos/farmacología , Hormona Liberadora de Corticotropina , Interacciones Farmacológicas , Estradiol/análogos & derivados , Estradiol/farmacología , Femenino , Ovariectomía/métodos , Oxitocina/sangre , Toxina del Pertussis/farmacología , Radioinmunoensayo/métodos , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT1A/metabolismo , Agonistas de Receptores de Serotonina/farmacología

RESUMEN

Transglutaminase (TGase)-induced activation of small G proteins via 5-hydroxytryptamine (HT)(2A) receptor signaling leads to platelet aggregation (Cell 115:851-862, 2003). We hypothesize that stimulation of 5-HT(2A) receptors in neurons activates TGase, resulting in transamidation of serotonin to a small G protein, Rac1, thereby constitutively activating Rac1. Using immunoprecipitation and immunoblotting, we show that, in rat cortical cell line A1A1v, serotonin increases TGase-catalyzed transamidation of Rac1. This transamidation occurs in both undifferentiated and differentiated cells. Treatment with a 5-HT(2A/2C) receptor agonist 2,5-dimethoxy-4-iodoamphetamine, but not the 5-HT(1A) receptor agonist 5-hydroxy-2-dipropylamino tetralin, increases transamidation of Rac1 by TGase. In A1A1v cells, 5-HT(2A) receptors mediate the transamidation reaction because expression of 5-HT(2C) receptors was not detectable and the selective 5-HT(2A) receptor antagonist blocked transamidation. Time course studies demonstrate that transamidation of Rac1 is significantly elevated after 5 and 15 min of serotonin treatment, but returns it to control levels after 30 min. The activity of Rac1 is also transiently increased following serotonin stimulation. Inhibition of TGase by cystamine or small interfering RNA reduces TGase modification of Rac1, and cystamine also prevents Rac1 activation. Serotonin itself is bound to Rac1 by TGase following 5-HT(2A) receptor stimulation as demonstrated by coimmunoprecipitation experiments and a dose-dependent decrease of serotonin-associated Rac1 by cystamine. These data support the hypothesis that Rac1 activity is transiently increased due to TGase-catalyzed transamidation of serotonin to Rac1 via stimulation of 5-HT(2A) receptors. Activation of Rac1 via TGase is a novel effector and second messenger of the 5-HT(2A) receptor-signaling cascade in neurons.

Asunto(s)

Receptor de Serotonina 5-HT2A/metabolismo , Transglutaminasas/metabolismo , Proteína de Unión al GTP rac1/metabolismo , Aminoaciltransferasas/genética , Aminoaciltransferasas/metabolismo , Animales , Catálisis/efectos de los fármacos , Células Cultivadas , Humanos , Ratas , Receptor de Serotonina 5-HT2A/genética , Serotonina/metabolismo , Serotonina/farmacología , Agonistas del Receptor de Serotonina 5-HT2 , Transglutaminasas/genética , Proteína de Unión al GTP rac1/genética

RESUMEN

The mechanisms underlying desensitization of serotonin 2A (5-HT(2A)) receptor signaling by antagonists are unclear but may involve changes in gene expression mediated via signal transduction pathways. In cells in culture, olanzapine causes desensitization of 5-HT(2A) receptor signaling and increases the levels of regulators of G protein signaling (RGS) 7 protein dependent on phosphorylation/activation of the Janus kinase 2 (Jak2)/signal transducers and activators of transcription 3 (Stat3) signaling pathway. In the current study, the 5-HT(2A) receptor signaling system in rat frontal cortex was examined following 7 days of daily treatment with 0.5, 2.0 or 10.0 mg/kg i.p. olanzapine. Olanzapine increased phosphorylation of Stat3 in rats treated daily with 10 mg/kg olanzapine and caused a dose-dependent desensitization of 5-HT(2A) receptor-mediated phospholipase C activity. There were dose-dependent increases in the levels of membrane-associated 5-HT(2A) receptor, G(alpha11) and G(alphaq) protein levels but no changes in the G(beta) protein levels. With olanzapine treatment, RGS4 protein levels increase in the membrane-fraction and decrease in the cytosolic fraction by similar amounts suggesting a redistribution of RGS4 protein within neurons. RGS7 protein levels increase in both the membrane and cytosolic fractions in rats treated daily with 10mg/kg olanzapine. The olanzapine-induced increase in Stat3 activity could underlie the increase in RGS7 protein expression in vivo as previously demonstrated in cultured cells. Furthermore, the increases in membrane-associated RGS proteins could play a role in desensitization of signaling by terminating the activated G(alphaq/11) proteins more rapidly.

Asunto(s)

Benzodiazepinas/farmacología , Lóbulo Frontal/fisiología , Receptor de Serotonina 5-HT2A/metabolismo , Factor de Transcripción STAT3/fisiología , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Animales , Membrana Celular/enzimología , Citosol/enzimología , Lóbulo Frontal/efectos de los fármacos , Proteínas de Unión al GTP/metabolismo , Masculino , Olanzapina , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT2A/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Fosfolipasas de Tipo C/metabolismo

RESUMEN

We previously reported that treatment and withdrawal from cocaine increases: (1) 5-HT2A receptor-mediated neuroendocrine responses, and (2) Galphaq and Galpha11 G-protein levels in the hypothalamic paraventricular nucleus (PVN) at 48 h post-treatment. This study investigates changes in the initial 24 h of withdrawal to discern whether 5-HT2A receptor supersensitivity is due to cocaine treatment or is induced during the withdrawal period. We report here increases in 5-HT2A receptor-mediated neuroendocrine responses only 12 or 24 h post-treatment, but not during the initial 4 h withdrawal period. Levels of membrane- or cytosol-associated Galphaq or Galpha11 proteins in PVN are not altered during the first 24 h of withdrawal. However, the density of 125I-(-)-1-(2,5 dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI)-labeled high-affinity 5-HT2A receptors in PVN increased 35% in rats withdrawn from cocaine for 24 h. These findings demonstrate that cocaine-induced increases in 5-HT2A receptor function in PVN represents a withdrawal-induced phenomena that: (1) is likely attributed to increased G-protein coupled/high-affinity conformational state of the 5-HT2A receptor, and (2) occurs in the absence of changes in the levels of associated G proteins during the first 24 h.

Asunto(s)

Cocaína/farmacología , Inhibidores de Captación de Dopamina/farmacología , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Receptor de Serotonina 5-HT2A/metabolismo , Anfetaminas/farmacocinética , Animales , Western Blotting/métodos , Corticosterona/sangre , Interacciones Farmacológicas , Subunidades alfa de la Proteína de Unión al GTP/metabolismo , Isótopos de Yodo/farmacocinética , Masculino , Núcleo Hipotalámico Paraventricular/metabolismo , Unión Proteica/efectos de los fármacos , Radioinmunoensayo/métodos , Ratas , Ratas Sprague-Dawley , Agonistas de Receptores de Serotonina/farmacocinética , Síndrome de Abstinencia a Sustancias/metabolismo , Factores de Tiempo

RESUMEN

Desensitization of post-synaptic serotonin1A (5-HT1A) receptors may underlie the clinical improvement of neuropsychiatric disorders. In the hypothalamic paraventricular nucleus, Galphaz proteins mediate the 5-HT1A receptor-stimulated increases in hormone release. Regulator of G protein signaling-Z1 (RGSZ1) is a GTPase-activating protein selective for Galphaz proteins. RGSZ1 regulates the duration of interaction between Galphaz proteins and effector systems. The present investigation determined the levels of RGSZ1 in the hypothalamic paraventricular nucleus of rats subjected to four different treatment protocols that produce desensitization of 5-HT1A receptors. These protocols include: daily administration of beta estradiol 3-benzoate (estradiol) for 2 days; daily administration of fluoxetine for 3 and 14 days; daily administration of cocaine for 7 or 14 days; and acute administration of (+/-)-1-(2,5 dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI; a 5-HT2A/2C receptor agonist). Estradiol treatment was the only protocol that increased the levels of RGSZ1 protein in the hypothalamic paraventricular nucleus in a dose-dependent manner (46%-132% over control). Interestingly, previous experiments indicate that only estradiol produces a decreased Emax of 5-HT1A receptor-stimulation of hormone release, whereas fluoxetine, cocaine and DOI produce a shift to the right (increased ED50). Thus, the desensitization of 5-HT1A receptors by estradiol might be attributable to increased levels of RGSZ1 protein. These findings may provide insight into the adaptation of 5-HT1A receptor signaling during pharmacotherapies of mood disorders in women and the well-established gender differences in the vulnerability to depression.

Asunto(s)

Estrógenos/farmacología , Proteínas Activadoras de GTPasa/efectos de los fármacos , Proteínas Activadoras de GTPasa/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Proteínas RGS/metabolismo , Receptor de Serotonina 5-HT1A/efectos de los fármacos , Adaptación Fisiológica/efectos de los fármacos , Adaptación Fisiológica/fisiología , Animales , Química Encefálica/genética , Cocaína/farmacología , Trastorno Depresivo/genética , Trastorno Depresivo/metabolismo , Trastorno Depresivo/fisiopatología , Relación Dosis-Respuesta a Droga , Resistencia a Medicamentos , Estrógenos/metabolismo , Femenino , Predisposición Genética a la Enfermedad/genética , Masculino , Proteínas de la Membrana/efectos de los fármacos , Proteínas del Tejido Nervioso/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Proteínas RGS/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT1A/metabolismo , Serotonina/metabolismo , Agonistas de Receptores de Serotonina/farmacología , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Caracteres Sexuales , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/fisiología

RESUMEN

This study examined the time course and possible mechanisms of agonist-induced desensitization of 5-hydroxytryptamine serotonin 2A receptors in the rat frontal cortex and hypothalamic paraventricular nucleus after 1, 4, and 7 days of treatment with (-)-1-(2,5-dimethoxy-4-iodophenyl)2-aminopropane HCl [(-)-DOI] (1 mg/kg i.p.), a selective 5-HT(2A/2C) receptor agonist. In the frontal cortex, 5-HT-mediated phospholipase C (PLC) enzyme activity decreased by 24 to 30% after 4 to 7 days of (-)-DOI treatment without any significant changes in the guanosine 5'-3-O-(thio)triphosphate-mediated PLC enzyme activity. Additionally, treatment with (-)-DOI did not significantly change the levels of G(alpha11), regulator of G protein signaling (RGS)4, or RGS7 proteins in the frontal cortex, whereas G(alphaq) protein levels in the frontal cortex decreased (47%) only after 7 daily (-)-DOI injections. The functional status of 5-HT(2A) receptors in the hypothalamic paraventricular nucleus was examined using 5-HT(2A) receptor-mediated increases in plasma hormone levels. Plasma adrenocorticotrophic hormone (ACTH) and oxytocin measurements showed that 5-HT(2A) receptor desensitization began after only 1 day of (-)-DOI treatment, and the desensitization continued to increase after 4 and 7 days of treatment (ACTH response decreased 64.2-67.7%; oxytocin response decreased 82.3-90.1%). There were no significant alterations in levels of G(alphaq) or G(alpha11) lamic paraventricular proteins in the hypothanucleus. In conclusion, these results suggest that chronically administered (-)-DOI induces desensitization of 5-HT(2A) receptors in vivo, via a reduction in the ability of 5-HT(2A) receptors to activate G proteins without consistently altering levels of G(alpha) proteins or RGS proteins.

Asunto(s)

Anfetaminas/farmacología , Hipotálamo/efectos de los fármacos , Corteza Prefrontal/efectos de los fármacos , Receptor de Serotonina 5-HT2A/metabolismo , Agonistas de Receptores de Serotonina/farmacología , Animales , Peso Corporal/efectos de los fármacos , Hipotálamo/metabolismo , Masculino , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Corteza Prefrontal/metabolismo , Ratas , Ratas Sprague-Dawley , Transducción de Señal/efectos de los fármacos , Fosfolipasas de Tipo C/metabolismo

RESUMEN

Differential adaptive changes in serotonin2A [5-hydroxytryptamine (5-HT)2A] receptor signaling during treatment may be one mechanism involved in the latency of therapeutic improvement with antidepressants, such as fluoxetine. We examined the effects of fluoxetine (2, 3, 7, 21, or 42 days) on hypothalamic 5-HT2A receptor signaling. The hormone responses to an injection of the 5-HT2A receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI) were used as an index of hypothalamic 5-HT2A receptor function. Treatment with fluoxetine for 21 or 42 days produced diminished adrenocorticotropic hormone (ACTH) and oxytocin (but not corticosterone) responses to DOI injections (2.5 mg/kg i.p.; 15 min postinjection). Regulators of G protein signaling 4 and Galphaq protein levels in the hypothalamic paraventricular nucleus were not altered during fluoxetine treatment. Because previous studies indicate that treatment with fluoxetine for 21 days resulted in increased hormone responses to DOI when measured at 30 min after injection, we examined the effect of fluoxetine (21 days) on DOI-induced increase hormone levels at 15, 30, and 60 min after DOI injection. Fluoxetine decreased the oxytocin response at 15 but not at 30 min post-DOI injection, and potentiated the ACTH and corticosterone responses at 30 min post-DOI injection. For comparison, we examined the effect of fluoxetine on 5-HT2A receptor-mediated increase in phospholipase C (PLC) activity in the frontal cortex. 5-HT-stimulated, but not guanosine 5'-O-(3-thio)triphosphate-stimulated PLC activity was increased after 21 days of fluoxetine-treatment. Overall, these results indicate that chronic fluoxetine treatment can potentiate 5-HT2A receptor signaling in frontal cortex but differentially alters 5-HT2A receptor signaling in oxytocin-containing neurons and corticotropin-releasing factor-containing neurons in the paraventricular nucleus.

Asunto(s)

Fluoxetina/farmacología , Indofenol/análogos & derivados , Neuronas/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/citología , Corteza Prefrontal/efectos de los fármacos , Receptores de Serotonina/metabolismo , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Animales , Peso Corporal/efectos de los fármacos , Hormona Liberadora de Corticotropina/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gq-G11 , Proteínas de Unión al GTP Heterotriméricas/metabolismo , Indofenol/farmacología , Masculino , Neuronas/metabolismo , Oxitocina/metabolismo , Corteza Prefrontal/metabolismo , Proteínas RGS/metabolismo , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT2A , Receptores de Serotonina/efectos de los fármacos , Transducción de Señal/fisiología , Factores de Tiempo , Fosfolipasas de Tipo C/metabolismo

RESUMEN

The 5-hydroxytryptamine(2A) and (2C) (5-HT(2A) and 5-HT(2C)) receptors are so closely related that selective agonists have not been developed until recently with the advent of (S)-2-(chloro-5-fluoro-indol-l-yl)-1-methylethylamine fumarate (Ro 60-0175), a putatively selective 5-HT(2C) receptor agonist. In the present study, Ro 60-0175 was used to analyze the importance of 5-HT(2C) receptors in hormone secretion. Injection of Ro 60-0175 (5 mg/kg s.c.) produced a maximum increase in plasma levels of adrenocorticotrophic hormone, oxytocin, and prolactin at 15 min postinjection and a maximum increase in plasma corticosterone levels at 60 min postinjection. Ro 60-0175-mediated increases in plasma hormone levels were dose-dependent (corticosterone ED(50) = 2.43 mg/kg; oxytocin ED(50) = 4.19 mg/kg; and prolactin ED(50) = 4.03 mg/kg). To assess the role of 5-HT(2C) and 5-HT(2A) receptors in mediating the hormone responses to Ro 60-0175, rats were pretreated with the 5-HT(2C) antagonist 6-chloro-5-methyl-1-[2-(2-methylpyridyl-3-oxy)-pyrid-5-yl carbonyl] indoline (SB 242084) or 5-HT(2A) antagonists (+/-)-2,3-dimethoxyphenyl-1-[2-4-(piperidine)-methanol] (MDL 100,907) before injection of Ro 60-0175 (5 mg/kg s.c.). Neither SB 242084 (0.1, 0.5, 1, and 5 mg/kg i.p.) nor MDL 100,907 (1, 5, and 10 microg/kg s.c.) significantly inhibited the Ro 60-0175-induced increases in plasma hormone levels. The data suggest that Ro 60-0175 increases hormone secretion by mechanisms independent of the activation of 5-HT(2C) and/or 5-HT(2A) receptors and suggest that Ro 60-0175 is not a highly selective 5-HT(2C) receptor agonist.

Asunto(s)

Etilaminas/farmacología , Indoles/farmacología , Receptores de Serotonina/metabolismo , Agonistas de Receptores de Serotonina/farmacología , Aminopiridinas/farmacología , Animales , Interacciones Farmacológicas , Fluorobencenos/farmacología , Masculino , Piperidinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT2A , Receptor de Serotonina 5-HT2C , Antagonistas de la Serotonina/farmacología , Factores de Tiempo

RESUMEN

Although women constitute the majority of patients who receive treatment with selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, most animal studies of SSRIs are conducted on males. The present study investigated whether long-term treatment of cycling female rats with fluoxetine alters their estrous cycle and the sensitivity of hypothalamic serotonin (5-HT) 5-HT(1A) and 5-HT(2A) receptor systems. Adult female rats received daily injections of fluoxetine (10 mg/kg, i.p.) for three consecutive estrous cycles (15.2+/-0.2 days) with the first injection beginning on metestrus (when circulating estrogen levels are low and stable). Fluoxetine did not alter basal plasma estradiol levels at metestrus, nor did it alter the pattern of estrous cyclicity. Rats treated with fluoxetine showed a loss in body weight. On the morning of metestrus of the fourth cycle (18 h after the last fluoxetine injection), the rats were injected with a sub-maximal dose of the 5-HT(1A) agonist (+/-)-8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT, 50 MICRO/kg, s.c.) or a maximal dose of the 5-HT(2A) agonist [(+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl] (DOI). Plasma levels of oxytocin, ACTH and corticosterone were measured as peripheral indicators of hypothalamic 5-HT(1A) and 5-HT(2A) receptor sensitivity. Injecting 8-OH-DPAT to saline pretreated rats produced a significant increase in plasma oxytocin (299%), ACTH (1456%) and corticosterone (170%) levels but not in plasma prolactin or renin concentrations. Greater increases in plasma levels of these hormones were observed after injecting DOI. Fluoxetine treatment completely blocked the oxytocin, ACTH and corticosterone responses to 8-OH-DPAT, but did not inhibit the effect of DOI on any hormone, thus confirming that fluoxetine treatment did not produce a deficit in the functioning of corticotropin releasing hormone or oxytocin containing neurons. These results indicate that in cycling female rats, fluoxetine treatment desensitizes hypothalamic post-synaptic 5-HT(1A) receptor signaling. Understanding the pharmacological effects of fluoxetine in females may lead to more effective treatment of women with mood disorders.

Asunto(s)

Antidepresivos de Segunda Generación/farmacología , Fluoxetina/farmacología , Hipotálamo/efectos de los fármacos , Receptores de Serotonina/efectos de los fármacos , 2,5-Dimetoxi-4-Metilanfetamina/farmacología , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Análisis de Varianza , Animales , Peso Corporal/efectos de los fármacos , Corticosterona/sangre , Interacciones Farmacológicas , Ciclo Estral/efectos de los fármacos , Ciclo Estral/metabolismo , Femenino , Hipotálamo/metabolismo , Hormonas Hipofisarias/sangre , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT2A , Receptores de Serotonina/metabolismo , Receptores de Serotonina 5-HT1 , Agonistas de Receptores de Serotonina/farmacología

RESUMEN

Desensitization of 5-HT(1A) receptors could be involved in the long-term therapeutic effect of anxiolytic and antidepressant drugs. Pretreatment of rats with the 5-HT(2A/2C) agonist DOI induces an attenuation of hypothalamic 5-HT(1A) receptor-G(z)-protein signaling, measured as the ACTH and oxytocin responses to an injection of the 5-HT(1A) agonist 8-OH-DPAT. We characterized this functional heterologous desensitization of 5-HT(1A) receptors in rats and examined some of the mechanisms that are involved. A time course experiment revealed that DOI produces a delayed and reversible reduction of the ACTH and oxytocin responses to an 8-OH-DPAT challenge. The maximal desensitization occurred at 2 hr, and it disappeared 24 hr after DOI injection. The desensitization was dose-dependent, and it shifted the oxytocin and ACTH dose-response curves of 8-OH-DPAT to the right (increased ED(50)) with no change in their maximal responses (E(max)). The 5-HT(2A) receptor antagonist MDL 100,907 prevented the DOI-induced desensitization, indicating that 5-HT(2A) receptors mediate the effect of DOI. Analysis of the components of the 5-HT(1A) receptor-G(z)-protein signaling system showed that DOI did not alter the level of membrane-associated G(z)-proteins in the hypothalamus. Additionally, DOI did not alter the binding of [(3)H]8-OH-DPAT or the inhibition by GTPgammaS of [(3)H]8-OH-DPAT binding in the hypothalamus. In conclusion, the activation of 5-HT(2A) receptors induces a transient functional desensitization of 5-HT(1A) receptor signaling in the hypothalamus, which may occur distal to the 5-HT(1A) receptor-G(z)-protein interface.

Asunto(s)

Hipotálamo/metabolismo , Receptores de Serotonina/metabolismo , 8-Hidroxi-2-(di-n-propilamino)tetralin/antagonistas & inhibidores , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Hormona Adrenocorticotrópica/sangre , Anfetaminas/farmacología , Animales , Unión Competitiva/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Fluorobencenos/farmacología , Proteínas de Unión al GTP/metabolismo , Guanosina 5'-O-(3-Tiotrifosfato)/farmacología , Hipotálamo/efectos de los fármacos , Masculino , Proteínas de la Membrana/metabolismo , Oxitocina/sangre , Piperidinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptor de Serotonina 5-HT2A , Receptores de Serotonina/efectos de los fármacos , Receptores de Serotonina 5-HT1 , Antagonistas de la Serotonina/farmacología , Agonistas de Receptores de Serotonina/farmacología

RESUMEN

Axonal signals activate myelinogenesis via regulation of the extent to which oligodendrocyte (OLG) processes wrap around the axon. The cytoskeleton in OLG processes is actively involved in myelination and is a putative target for axonal regulation of myelination. The axon-associated neuregulins may regulate the cytoskeleton extensions in OLG processes. Here, we report that the neuregulin neu differentiation factor (NDF) increases the expression of tau mRNA and tau protein in OLGs. Treatment of neonatal OLGs with alpha-NDF or beta-NDF resulted in dramatic increases in the length of OLG processes, which appeared either as singular unbranched extensions or as a network of extensively branched processes. By immunoblot analysis with tau-1 mAb, which recognizes the dephosphorylated form of the tau proteins, neonatal OLGs treated with alpha-NDF or beta-NDF, had an increase in tau protein levels. The increase of tau levels in beta-NDF-treated cells is much greater than the twofold increase present in alpha-NDF-treated cells. By immunoblot analysis with the phosphorylation-insensitive tau-5 mAb, beta-NDF-treated cells had a twofold increase in tau. Immunoblot analysis suggest that alpha-NDF and beta-NDF promote a twofold increase in the tau protein levels in OLG, with the beta-factor also promoting a tau dephosphorylation. Using promoters spanning the amino-terminal region of tau, we found that OLGs treated with alpha-NDF or beta-NDF contained approximately twofold more tau mRNA than untreated cells. However, there was no qualitative difference between control and NDF-treated cells in the pattern of tau mRNA isoforms expressed. A model is proposed in which the axonal NDF-induced regulation of tau expression in OLGs may be part of the mechanism by which the axon regulates myelination.

Asunto(s)

Animales Recién Nacidos/crecimiento & desarrollo , Diferenciación Celular/fisiología , Sistema Nervioso Central/crecimiento & desarrollo , Neurregulina-1/metabolismo , Oligodendroglía/metabolismo , ARN Mensajero/metabolismo , Proteínas tau/metabolismo , Animales , Animales Recién Nacidos/anatomía & histología , Animales Recién Nacidos/metabolismo , Axones/efectos de los fármacos , Axones/metabolismo , Axones/ultraestructura , Diferenciación Celular/efectos de los fármacos , Células Cultivadas/citología , Células Cultivadas/efectos de los fármacos , Células Cultivadas/metabolismo , Sistema Nervioso Central/citología , Sistema Nervioso Central/metabolismo , Técnica del Anticuerpo Fluorescente , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/fisiología , Vaina de Mielina/efectos de los fármacos , Vaina de Mielina/metabolismo , Vaina de Mielina/ultraestructura , Neurregulina-1/farmacología , Oligodendroglía/citología , Oligodendroglía/efectos de los fármacos , Isoformas de Proteínas/efectos de los fármacos , Isoformas de Proteínas/metabolismo , Estructura Terciaria de Proteína/efectos de los fármacos , Estructura Terciaria de Proteína/fisiología , ARN Mensajero/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Proteínas tau/efectos de los fármacos , Proteínas tau/genética

RESUMEN

Tau is a family of microtubule-associated phosphoproteins in which isoform variation is produced by alternative splicing of a single gene and posttranslational modifications. Tau isoforms that include exon 10 are overexpressed in frontotemporal dementia and progressive supranuclear palsy. Therefore, we examined the expression of tau mRNA splice variants during axonal regeneration and abortive regeneration. Previous work in our laboratory demonstrated that expression of exon 10 tau isoforms during regeneration and abortive regeneration was altered and partially recapitulated the developmental patterns of tau isoform expression. Using RT-PCR, we examined the alternative splicing of exons 2 and 3 in tau during early postnatal development and regeneration in the rat spinal cord. The levels of tau lacking exons 2 and 3 were high on the day of birth and rapidly declined. Conversely, tau isoforms containing exon 2 or exons 2 and 3 first appeared at low levels and steadily increased. During axonal regeneration, the levels of all three tau mRNA isoforms were significantly lower 7 days after injury. In a model of abortive regeneration, all of the tau isoforms were elevated 14 and 42 days postinjury. The relative levels of exon 2 and 3 tau splice variants were not altered during regeneration or abortive regeneration as occurred during development. These results suggest that tau isoform expression following neuronal injury does not recapitulate the developmental pattern and is not independently regulated as in development. Our previous results together with these data suggest that alterations in tau mRNA isoform expression that occur in neurodegeneration are not secondary to axonal injury but may be a more primary event underlying cytoskeletal derangement.

Asunto(s)

Envejecimiento/metabolismo , Empalme Alternativo , ARN Mensajero/metabolismo , Médula Espinal/metabolismo , Proteínas tau/metabolismo , Empalme Alternativo/fisiología , Animales , Axones/metabolismo , Axotomía , Femenino , Masculino , Compresión Nerviosa , Regeneración Nerviosa , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Ratas , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Neuropatía Ciática/metabolismo , Proteínas tau/genética

RESUMEN

The neuropathological hallmarks of many neurodegenerative diseases are intraneuronal inclusions containing cytoskeletal proteins such as neurofilaments in Lewy bodies in Parkinson's disease and tau in neurofibrillary tangles in Alzheimer's disease. Dysfunction in dopaminergic and cholinergic systems also exist in both Alzheimer's disease and Parkinson's disease. Because the primary pathology in Parkinson's disease is localized to the dopaminergic system, we set out to determine if perturbations in cholinergic systems are a consequence of dopaminergic neuron loss. Therefore, following intracerebral microinjections of 6-hydroxydopamine in rats, the activity of cholinergic neurons was measured by hemicholinium binding in cholinergic terminal fields and perturbations in cytoskeletal proteins were examined in dopaminoceptive neurons using immunocytochemistry. The 6-hydroxydopamine injections robustly reduced the number of monoaminergic cell bodies in the lateral midbrain and dramatically decreased dopamine and its major metabolites in dopaminergic projection sites. This treatment increased hemicholinium binding in the prefrontal cortex (200%) and amygdala (284%); however, despite previous reports to the contrary, there were no increases in immunoreactivity for phosphorylated neurofilaments, microtubule-associated protein (MAP) 2, tau or paired helical filament (PHF) tau. This lack of an increase in cytoskeletal proteins was observed following either injections of moderate doses of the toxin directly into the medial forebrain bundle or after high doses were administered intracerebroventricularly. These results suggest that removal of dopaminergic inputs to the forebrain results in hyperactivity of the cholinergic systems but is not sufficient to induce postsynaptic perturbations in cytoskeletal proteins which occur in neurodegenerative diseases.

Asunto(s)

Encéfalo/fisiología , Proteínas del Citoesqueleto/metabolismo , Dopamina/metabolismo , Neuronas/fisiología , Receptores Dopaminérgicos/fisiología , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/fisiología , Animales , Encéfalo/efectos de los fármacos , Colinérgicos/farmacocinética , Lóbulo Frontal/efectos de los fármacos , Lóbulo Frontal/fisiología , Hemicolinio 3/farmacocinética , Masculino , Microinyecciones , Neuronas/efectos de los fármacos , Neuronas/patología , Especificidad de Órganos , Oxidopamina/administración & dosificación , Oxidopamina/toxicidad , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/fisiología , Ratas , Ratas Sprague-Dawley , Sinapsis/efectos de los fármacos , Sinapsis/fisiología

RESUMEN

The mechanisms leading to the abnormal self-polymerization of tau into straight and paired helical filaments (PHFs) and neurofibrillary tangles (NFT) in Alzheimer disease (AD) and progressive supranuclear palsy (PSP) are not known. However, transglutaminase-induced cross-linking of PHF-tau was observed in AD and thus may also contribute to the formation of NFT in other neurodegenerative disorders including PSP. Tissue homogenates from PSP and normal age-matched controls were used to immunoaffinity-purify proteins containing transglutaminase-induced epsilon-(gamma-glutamyl) lysine cross-links. The immunoaffinity-purified proteins were then examined on immunoblots with a PHF-tau antibody, PHF-1. There were significantly higher levels of epsilon-(gamma-glutamyl) lysine cross-linking of PHF-tau in globus pallidus and pons regions of PSP cases compared to barely detectable cross-links in controls. The occipital cortex, an area spared from neurofibrillary pathology in PSP, showed no detectable cross-linking of PHF-tau protein in either PSP cases or control cases. Double-label immunofluorescence demonstrated the colocalization of the cross-link and PHF-tau in NFT in pons of PSP Previous studies and present data are consistent with the hypothesis that transglutaminase-induced cross-linking may be a factor contributing to the abnormal polymerization and stabilization of tau in straight and PHFs leading to neurofibrillary tangle formation in neurodegenerative diseases, including PSP and AD.

Asunto(s)

Globo Pálido/metabolismo , Lóbulo Occipital/metabolismo , Puente/metabolismo , Parálisis Supranuclear Progresiva/metabolismo , Transglutaminasas/metabolismo , Proteínas tau/metabolismo , Anciano , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Reactivos de Enlaces Cruzados , Globo Pálido/patología , Humanos , Ovillos Neurofibrilares/metabolismo , Ovillos Neurofibrilares/patología , Puente/patología , Parálisis Supranuclear Progresiva/patología

RESUMEN

The present study investigated whether estrogen would desensitize hypothalamic serotonin(1A) (5-HT(1A)) receptors by examining the neuroendocrine response to 8-OH-DPAT, a 5-HT(1A) agonist. Rats were ovariectomized, allowed to recover for 5 days, then given 2 daily injections of estradiol benzoate or vehicle (10 microg/day, s.c.). Twenty-four hours after the second injection, rats were challenged with a sub-maximal dose of 8-OH-DPAT (50 microg/kg, sc) or saline 15 min prior to sacrifice. 8-OH-DPAT produced a significant increase in plasma oxytocin, ACTH and corticosterone levels in ovariectomized rats. While estrogen treatment for 2 days did not alter basal hormone levels, it did significantly reduce the magnitude of oxytocin, ACTH and corticosterone responses to 8-OH-DPAT. The reduction in hormone responses was accompanied by a significant reduction in hypothalamic levels of G(z), G(i1) and G(i3) proteins (by 50%, 30% and 50%, respectively). These findings suggest that a reduction in these G proteins may contribute to the mechanisms underlying estrogen-induced desensitization of 5-HT(1A) receptors. The desensitization of 5-HT(1A) receptors has been suggested to underlie the therapeutic effects of antidepressant 5-HT uptake inhibitors (SSRIs). Thus, the present results suggest that estrogen or estrogen-like substances in combination with SSRIs may prove effective in developing novel therapeutic strategies for neuropsychiatric disorders in women.

Asunto(s)

Estrógenos/farmacología , Subunidades alfa de la Proteína de Unión al GTP Gi-Go/metabolismo , Subunidades alfa de la Proteína de Unión al GTP , Proteínas de Unión al GTP Heterotriméricas/metabolismo , Hipotálamo/efectos de los fármacos , Receptores de Serotonina/efectos de los fármacos , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Hormona Adrenocorticotrópica/sangre , Hormona Adrenocorticotrópica/efectos de los fármacos , Animales , Corticosterona/sangre , Femenino , Hipotálamo/metabolismo , Ovariectomía , Oxitocina/sangre , Oxitocina/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Receptores de Serotonina/metabolismo , Receptores de Serotonina 5-HT1

RESUMEN

Treatment with selective serotonin reuptake inhibitors induces a desensitization of hypothalamic postsynaptic 5-hydroxytryptamine (5-HT)(1A) receptors in humans and rats. This study investigated whether fluoxetine-induced desensitization is due to overactivation of postsynaptic 5-HT(1A) receptors; whether blockade of somatodendritic 5-HT(1A) autoreceptors accelerates this desensitization; and whether desensitization is associated with a reduction of Gz proteins, which couple to 5-HT(1A) receptors. WAY-100635 was tested at low doses (0.03-0.3 mg/kg), which antagonize somatodendritic 5-HT(1A) autoreceptors in the raphe nuclei, and at a higher dose (1 mg/kg), which completely blocks postsynaptic 5-HT(1A) receptors. Plasma levels of oxytocin and adrenal corticotrophic hormone (corticotropin) were measured as peripheral indicators of hypothalamic 5-HT(1A) receptor function. Daily injections of fluoxetine (10 mg/kg/day i.p.) for 2 days did not desensitize 5-HT(1A) receptors but three daily injections of fluoxetine produced a partial desensitization of the hormone responses to (+/-)-8-hydroxy-2-dipropylaminoetetralin (50 microg/kg s.c.). WAY-100635 (0.03-0.3 mg/kg) did not accelerate or potentiate the fluoxetine-induced desensitization of 5-HT(1A) receptors. However, WAY-100635 at a dose that completely blocks postsynaptic 5-HT(1A) receptors (1.0 mg/kg) completely prevented the fluoxetine-induced desensitization of 5-HT(1A) receptors. These data demonstrate that at least 3 days of fluoxetine exposure is required to produce a homologous desensitization of hypothalamic 5-HT(1A) receptors. Although previous studies indicate that injections of fluoxetine for 14 days produce a reduction of Gz protein levels in the hypothalamus, the levels of Gz proteins were not affected by either fluoxetine or WAY-100635. Alternative mechanisms mediating the initial stages of 5-HT(1A) receptor desensitization could involve post-translational modifications in the 5-HT(1A) receptor-Gz protein-signaling cascade.

Asunto(s)

Fluoxetina/farmacología , Hipotálamo/efectos de los fármacos , Piperazinas/farmacología , Piridinas/farmacología , Receptores de Serotonina/efectos de los fármacos , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Hormona Adrenocorticotrópica/sangre , Animales , Subunidades alfa de la Proteína de Unión al GTP Gi-Go/análisis , Masculino , Oxitocina/sangre , Ratas , Ratas Sprague-Dawley , Receptores de Serotonina 5-HT1 , Antagonistas de la Serotonina/farmacología

RESUMEN

Using in situ hybridization and immunoblot analysis, the present studies identified G(z) mRNA and G(z)-protein in the hypothalamic paraventricular nucleus. The role of G(z)-proteins in hypothalamic 5-HT(1A) receptor signaling was examined in vivo. Activation of 5-HT(1A) receptors increases the secretion of oxytocin and ACTH, but not prolactin. Intracerebroventricular infusion (3-4 d) of G(z) antisense oligodeoxynucleotides, with different sequences and different phosphorothioate modification patterns, reduced the levels of G(z)-protein in the hypothalamic paraventricular nucleus, whereas missense oligodeoxynucleotides had no effect. Neither antisense nor missense oligodeoxynucleotide treatment altered basal plasma levels of ACTH, oxytocin, or prolactin, when compared with untreated controls. An antisense-induced decrease in hypothalamic G(z)-protein levels was paralleled by a significant decrease in the oxytocin and ACTH responses to the 5-HT(1A) agonist 8-hydroxy-dipropylamino-tetralin (8-OH-DPAT). In contrast, the prolactin response to 8-OH-DPAT (which cannot be blocked by 5-HT(1A) antagonists) was not inhibited by G(z) antisense oligodeoxynucleotides. G(z)-proteins are the only members of the G(i)/G(o)-protein family that are not inactivated by pertussis toxin. In a control experiment, pertussis toxin treatment (1 microgram/5 microliter, i.c.v.; 48 hr before the 8-OH-DPAT challenge) did not inhibit the ACTH response, potentiated the oxytocin response, and eliminated the prolactin response to 8-OH-DPAT. Thus, pertussis toxin-sensitive G(i)/G(o)-proteins do not mediate the 5-HT(1A) receptor-mediated increase in ACTH and oxytocin secretion. Combined, these studies provide the first in vivo evidence for a key role of G(z)-proteins in coupling hypothalamic 5-HT(1A) receptors to effector mechanisms.

Asunto(s)

Hormona Adrenocorticotrópica/metabolismo , Subunidades alfa de la Proteína de Unión al GTP , Proteínas de Unión al GTP Heterotriméricas/fisiología , Oxitocina/metabolismo , Núcleo Hipotalámico Paraventricular/fisiología , Receptores de Serotonina/fisiología , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Hormona Adrenocorticotrópica/efectos de los fármacos , Animales , Proteínas de Unión al GTP Heterotriméricas/efectos de los fármacos , Hipotálamo/efectos de los fármacos , Hipotálamo/fisiología , Masculino , Oligonucleótidos Antisentido/farmacología , Oxitocina/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Toxina del Pertussis , Prolactina/efectos de los fármacos , Prolactina/metabolismo , ARN Mensajero/efectos de los fármacos , ARN Mensajero/metabolismo , Ratas , Receptores de Serotonina/efectos de los fármacos , Receptores de Serotonina 5-HT1 , Agonistas de Receptores de Serotonina/farmacología , Factores de Virulencia de Bordetella/farmacología