RESUMEN
Previous studies from our laboratory have shown sex differences in the behavioral, molecular, and neurochemical manifestations of morphine withdrawal and they were related to an increased sensitivity to morphine effects in males. In addition, we observed an interaction between the GABAergic and opioid systems that could also be sex-dependent. Baclofen, a GABAB receptor agonist, prevented the somatic expression and the molecular and neurochemical changes induced by morphine withdrawal syndrome in mice. On the contrary, little is known about baclofen effects in the rewarding properties of morphine in male and female mice. The present study aimed to explore the effect of baclofen (1, 2 and 3 mg/kg, i.p.) pretreatment in the rewarding effects induced by morphine (7 mg/kg, s.c.) and its effect on c-Fos and brain-derived neurotrophic factor (BDNF) expression induced by the rewarding properties of morphine in prepubertal male and female mice. Baclofen (2 mg/kg) pretreatment prevented the rewarding effects of morphine only in male mice, while baclofen (3 mg/kg) reduced these effects in both sexes. Moreover, the rewarding effects of morphine were associated with a decrease of BDNF and c-Fos expression cingulate cortex, nucleus accumbens shell, cornu ammonis 1 (CA1), and cornu ammonis 3 (CA3) areas of the hippocampus only in male mice. In addition, baclofen pretreatment prevented these changes in BDNF, but not in c-Fos expression. In conclusion, our results show that GABAB receptors have a regulatory role in the rewarding effects of morphine that could be of interest for a potential future therapeutic application in opioid use disorders.
Asunto(s)
Baclofeno , Factor Neurotrófico Derivado del Encéfalo , Morfina , Proteínas Proto-Oncogénicas c-fos , Recompensa , Animales , Baclofeno/farmacología , Masculino , Femenino , Morfina/farmacología , Ratones , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Agonistas de Receptores GABA-B/farmacología , Caracteres Sexuales , Conducta Animal/efectos de los fármacos , Factores SexualesRESUMEN
Type-A and -B GABA receptors (GABAARs/GABABRs) control brain function and behaviour by fine tuning neurotransmission. Over-time these receptors have become important therapeutic targets for treating neurodevelopmental and neuropsychiatric disorders. Several positive allosteric modulators (PAMs) of GABARs have reached the clinic and selective targeting of receptor subtypes is crucial. For GABABRs, CGP7930 is a widely used PAM for in vivo studies, but its full pharmacological profile has not yet been established. Here, we reveal that CGP7930 has multiple effects not only on GABABRs but also GABAARs, which for the latter involves potentiation of GABA currents, direct receptor activation, and also inhibition. Furthermore, at higher concentrations, CGP7930 also blocks G protein-coupled inwardly-rectifying K+ (GIRK) channels diminishing GABABR signalling in HEK 293 cells. In male and female rat hippocampal neuron cultures, CGP7930 allosteric effects on GABAARs caused prolonged rise and decay times and reduced the frequency of inhibitory postsynaptic currents and potentiated GABAAR-mediated tonic inhibition. Additional comparison between predominant synaptic- and extrasynaptic-isoforms of GABAAR indicated no evident subtype selectivity for CGP7930. In conclusion, our study of CGP7930 modulation of GABAARs, GABABRs and GIRK channels, indicates this compound is unsuitable for use as a specific GABABR PAM.
Asunto(s)
Canales de Potasio , Transmisión Sináptica , Ratas , Masculino , Humanos , Femenino , Animales , Células HEK293 , Ácido gamma-Aminobutírico , Receptores de GABA-B/metabolismoRESUMEN
Combining cell type-specific optogenetics and whole cell recordings on mouse acute hippocampal slices, we compared GABA release from cholecystokinin-expressing (CCK) and parvalbumin-expressing (PV) interneurons onto CA1 pyramidal neurons. Baclofen, a selective GABAB receptor agonist, inhibited GABAergic synaptic transmission greater from CCK terminals, compared to that from PV terminals. The N-type calcium channels on CCK and P/Q-type calcium channels on PV terminals contributed to the GABAB receptor-mediated inhibition, respectively. Our data thus provide direct evidence that GABAB receptors differentially modulate GABA release from CCK and PV interneurons, adding to an increasing list of differences between these two interneuron subtypes in modulating hippocampal pyramidal neurons.
Asunto(s)
Región CA1 Hipocampal/metabolismo , Interneuronas/metabolismo , Células Piramidales/metabolismo , Receptores de GABA-B/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Animales , Región CA1 Hipocampal/citología , Canales de Calcio Tipo N/metabolismo , Células Cultivadas , Colecistoquinina/genética , Colecistoquinina/metabolismo , Ratones , Parvalbúminas/genética , Parvalbúminas/metabolismoRESUMEN
Although the output of the lateral habenula (LHb) controls the activity of midbrain dopaminergic and serotonergic systems, which are implicated in the pathophysiology of anxiety, it is not known how blockade of GABAB receptors in the region affects anxiety-like behaviors, particularly in Parkinson's disease-related anxiety. In this study, unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta in rats induced anxiety-like behaviors, led to hyperactivity of LHb neurons and decreased the level of extracellular dopamine (DA) in the basolateral amygdala (BLA) compared to sham-lesioned rats. Intra-LHb injection of pre-synaptic GABAB receptor antagonist CGP36216 produced anxiolytic-like effects, while the injection of post-synaptic GABAB receptor antagonist CGP35348 induced anxiety-like responses in both groups. Further, intra-LHb injection of CGP36216 decreased the firing rate of the neurons, and increased the GABA/glutamate ratio in the LHb and release of DA and serotonin (5-HT) in the BLA; conversely, CGP35348 increased the firing rate of the neurons and decreased the GABA/glutamate ratio and release of DA and 5-HT in sham-lesioned and the lesioned rats. However, the doses of the antagonists producing these behavioral effects in the lesioned rats were lower than those in sham-lesioned rats, and the duration of action of the antagonists on the firing rate of the neurons and release of the neurotransmitters was prolonged in the lesioned rats. Collectively, these findings suggest that pre-synaptic and post-synaptic GABAB receptors in the LHb are involved in the regulation of anxiety-like behaviors, and degeneration of the nigrostriatal pathway up-regulates function and/or expression of these receptors.
Asunto(s)
Ansiedad/metabolismo , Complejo Nuclear Basolateral/metabolismo , Antagonistas de Receptores de GABA-B/farmacología , Habénula/metabolismo , Trastornos Parkinsonianos/metabolismo , Receptores de GABA-B/metabolismo , Receptores Presinapticos/metabolismo , Animales , Ansiedad/fisiopatología , Complejo Nuclear Basolateral/efectos de los fármacos , Complejo Nuclear Basolateral/fisiopatología , Conducta Animal/efectos de los fármacos , Dopamina/metabolismo , Habénula/efectos de los fármacos , Habénula/fisiopatología , Compuestos Organofosforados/farmacología , Oxidopamina/toxicidad , Trastornos Parkinsonianos/fisiopatología , Trastornos Parkinsonianos/psicología , Porción Compacta de la Sustancia Negra , Ácidos Fosfínicos/farmacología , Ratas , Receptores Presinapticos/antagonistas & inhibidores , Serotonina/metabolismo , Regulación hacia ArribaRESUMEN
Allosteric modulators of G protein coupled receptors (GPCRs), including GABABRs (GABABRs), are promising therapeutic candidates. While several positive allosteric modulators (PAM) of GABABRs have been characterized, only recently the first negative allosteric modulator (NAM) has been described. In the present study, we report the characterization of COR758, which acts as GABABR NAM in rat cortical membranes and CHO cells stably expressing GABABRs (CHO-GABAB). COR758 failed to displace the antagonist [3H]CGP54626 from the orthosteric binding site of GABABRs showing that it acts through an allosteric binding site. Docking studies revealed a possible new allosteric binding site for COR758 in the intrahelical pocket of the GABAB1 monomer. COR758 inhibited basal and GABABR-stimulated O-(3-[35Sthio)-triphosphate ([35S]GTPγS) binding in brain membranes and blocked the enhancement of GABABR-stimulated [35S]GTPγS binding by the PAM GS39783. Bioluminescent resonance energy transfer (BRET) measurements in CHO-GABAB cells showed that COR758 inhibited G protein activation by GABA and altered GABABR subunit rearrangements. Additionally, the compound altered GABABR-mediated signaling such as baclofen-induced inhibition of cAMP production in transfected HEK293 cells, agonist-induced Ca2+ mobilization as well as baclofen and the ago-PAM CGP7930 induced phosphorylation of extracellular signal-regulated kinases (ERK1/2) in CHO-GABAB cells. COR758 also prevented baclofen-induced outward currents recorded from rat dopamine neurons, substantiating its property as a NAM for GABABRs. Altogether, these data indicate that COR758 inhibits G protein signaling by GABABRs, likely by interacting with an allosteric binding-site. Therefore, COR758 might serve as a scaffold to develop additional NAMs for therapeutic intervention.
Asunto(s)
Moduladores del GABA/química , Moduladores del GABA/farmacología , Antagonistas de Receptores de GABA-B/química , Antagonistas de Receptores de GABA-B/farmacología , Receptores de GABA-B/fisiología , Regulación Alostérica/efectos de los fármacos , Regulación Alostérica/fisiología , Animales , Transferencia de Energía por Resonancia de Bioluminiscencia/métodos , Células CHO , Cricetulus , Relación Dosis-Respuesta a Droga , Agonistas de Receptores GABA-B/química , Agonistas de Receptores GABA-B/farmacología , Humanos , Masculino , Ratas , Ratas Sprague-Dawley , Ácido gamma-Aminobutírico/química , Ácido gamma-Aminobutírico/farmacologíaRESUMEN
Dopamine signaling in nucleus accumbens (NAc) is modulated by γ-aminobutyric acid (GABA), acting through GABA-A and GABA-B receptors: dysregulation of GABAergic control of dopamine function may be important in behavioral deficits in schizophrenia. We investigated the effect of GABA-A (muscimol) and GABA-B (baclofen) receptor agonists on electrically stimulated dopamine release. Furthermore, we explored whether drug-induced changes were disrupted by pretreatment with phencyclidine, which provides a well-validated model of schizophrenia. Using brain slices from female rats, fast-scan cyclic voltammetry was used to measure electrically stimulated dopamine release in NAc shell. Both muscimol and baclofen caused concentration-dependent attenuation of evoked dopamine release: neither effect was changed by dihydro-ß-erythroidine, a nicotinic acetylcholine receptor antagonist, or the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), precluding indirect mechanisms using these transmitter systems in the GABAergic actions. In slices taken from rats pretreated with phencyclidine, the attenuation of evoked dopamine release by baclofen was abolished, but the attenuation by muscimol was unaffected. Since phencyclidine pretreatment was followed by drug-free washout period of at least a week, the drug was not present during recording. Therefore, disruption of GABA-B modulation of dopamine is due to long-term functional changes resulting from the treatment, rather than transient changes due to the drug's presence at test. This enduring dysregulation of GABA-B modulation of accumbal dopamine release provides a plausible mechanism through which GABA dysfunction influences accumbal dopamine leading to behavioral changes seen in schizophrenia and may provide a route for novel therapeutic strategies to treat the condition.
Asunto(s)
Dopamina/metabolismo , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Esquizofrenia/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Animales , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Agonistas del GABA/farmacología , Fenciclidina/farmacología , Ratas , Ratas WistarRESUMEN
Somatodendritic dopamine (DA) release from midbrain DA neurons activates D2 autoreceptors on these cells to regulate their activity. However, the source of autoregulatory DA remains controversial. Here, we test the hypothesis that D2 autoreceptors on a given DA neuron in the substantia nigra pars compacta (SNc) are activated primarily by DA released from that same cell, rather than from its neighbors. Voltage-clamp recording allows monitoring of evoked D2-receptor-mediated inhibitory currents (D2ICs) in SNc DA neurons as an index of DA release. Single-cell application of antibodies to Na+ channels via the recording pipette decreases spontaneous activity of recorded neurons and attenuates evoked D2ICs; antibodies to SNAP-25, a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein, also decrease D2IC amplitude. Evoked D2ICs are nearly abolished by the light chain of botulinum neurotoxin A, which cleaves SNAP-25, whereas synaptically activated GABAB-receptor-mediated currents are unaffected. Thus, somatodendritic DA release in the SNc autoinhibits the neuron that releases it.
Asunto(s)
Dendritas/metabolismo , Dopamina/metabolismo , Sustancia Negra/metabolismo , Animales , Anticuerpos/metabolismo , Estimulación Eléctrica , Potenciales Postsinápticos Inhibidores , Cinética , Masculino , Ratones Endogámicos C57BL , Receptores de Dopamina D2/metabolismo , Análisis de la Célula Individual , Proteína 25 Asociada a Sinaptosomas/metabolismo , Canales de Sodio Activados por Voltaje/metabolismo , Ácido gamma-Aminobutírico/metabolismoRESUMEN
Resilience is the capacity to maintain normal psychological and physical functions in the face of stress and adversity. Understanding how one can develop and enhance resilience is of great relevance to not only promoting coping mechanisms but also mitigating maladaptive stress responses in psychiatric illnesses such as depression. Preclinical studies suggest that GABA(B) receptors (GABA(B1) and GABA(B2)) are potential targets for the treatment of major depression. In this study, we assessed the functional role of GABA(B) receptors in stress resilience and vulnerability by using a chronic unpredictable stress (CUS) model in mice. As the medial prefrontal cortex (mPFC) plays a key role in the top-down modulation of stress responses, we focused our study on this brain structure. Our results showed that only approximately 41.9% of subjects exhibited anxiety- or despair-like behaviors after exposure to CUS. The vulnerable mice showed higher c-Fos expression in the infralimbic cortex (IL) subregion of the mPFC when exposed to a social stressor. Moreover, the expression of GABA(B1) but not GABA(B2) receptors was significantly downregulated in IL subregion of susceptible mice. Finally, we found that intra-IL administration of baclofen, a GABA(B) receptor agonist, rapidly relieved the social avoidance symptoms of the "stress-susceptible" mice. Taken together, our results show that the GABA(B1) receptor within the IL may play an important role in stress resilience and vulnerability, and thus open an avenue to develop novel, personalized approaches to promote stress resilience and treat stress-related psychiatric disorders.
Asunto(s)
Ansiedad , Conducta Animal/fisiología , Agonistas de Receptores GABA-B/farmacología , Corteza Prefrontal , Receptores de GABA-A/metabolismo , Resiliencia Psicológica , Estrés Psicológico , Animales , Ansiedad/tratamiento farmacológico , Ansiedad/etiología , Ansiedad/metabolismo , Ansiedad/fisiopatología , Reacción de Prevención/efectos de los fármacos , Reacción de Prevención/fisiología , Baclofeno/farmacología , Conducta Animal/efectos de los fármacos , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades/metabolismo , Susceptibilidad a Enfermedades/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Corteza Prefrontal/fisiopatología , Conducta Social , Estrés Psicológico/complicaciones , Estrés Psicológico/tratamiento farmacológico , Estrés Psicológico/metabolismo , Estrés Psicológico/fisiopatologíaRESUMEN
Brain nicotinic acetylcholine receptors (nAChRs) reportedly suppress the micturition, but the mechanisms responsible for this suppression remain unclear. We previously reported that intracerebroventricularly administered (±)-epibatidine (non-selective nAChR agonist) activated the sympatho-adrenomedullary system, which can affect the micturition. Therefore, we investigated (1) whether intracerebroventricularly administered (±)-epibatidine-induced effects on the micturition were dependent on the sympatho-adrenomedullary system, and (2) brain nAChR subtypes involved in the (±)-epibatidine-induced effects in urethane-anesthetized male Wistar rats. Plasma noradrenaline and adrenaline (catecholamines) were measured just before and 5 min after (±)-epibatidine administration. Evaluation of urodynamic parameters, intercontraction intervals (ICI) and maximal voiding pressure (MVP) by cystometry was started 1 h before (±)-epibatidine administration or intracerebroventricular pretreatment with other drugs and continued 1 h after (±)-epibatidine administration. Intracerebroventricularly administered (±)-epibatidine elevated plasma catecholamines and prolonged ICI without affecting MVP, and these changes were suppressed by intracerebroventricularly pretreated mecamylamine (non-selective nAChR antagonist). Acute bilateral adrenalectomy abolished the (±)-epibatidine-induced elevation of plasma catecholamines, but had no effect on the (±)-epibatidine-induced ICI prolongation. The latter was suppressed by intracerebroventricularly pretreated methyllycaconitine (selective α7-nAChR antagonist), SR95531 (GABAA antagonist), and SCH50911 (GABAB antagonist), but not by dihydro-ß-erythroidine (selective α4ß2-nAChR antagonist). Intracerebroventricularly administered PHA568487 (selective α7-nAChR agonist) prolonged ICI without affecting MVP, similar to (±)-epibatidine. These results suggest that stimulation of brain α7-nAChRs suppresses the rat micturition through brain GABAA/GABAB receptors, independently of the sympatho-adrenomedullary outflow modulation.
Asunto(s)
Encéfalo/metabolismo , Receptores de GABA/metabolismo , Micción , Receptor Nicotínico de Acetilcolina alfa 7/metabolismo , Médula Suprarrenal/efectos de los fármacos , Médula Suprarrenal/metabolismo , Adrenalectomía , Animales , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Epinefrina/sangre , Masculino , Contracción Muscular/efectos de los fármacos , Norepinefrina/sangre , Piridinas/farmacología , Ratas Wistar , Sistema Nervioso Simpático/efectos de los fármacos , Sistema Nervioso Simpático/metabolismoRESUMEN
Resilience means "the ability to withstand or recover quickly in the face of adversity". Elucidating the neural and molecular mechanisms underlying stress resilience will facilitate the development of more effective treatments for stress-induced psychiatric disorders such as depression. The habenular nuclei, which consist of the medial and lateral sub-regions (MHb and LHb, respectively), have been described as a critical node in emotional regulations. GABA(B) receptors play an important regulatory role in habenular activity. In this study, we assessed the functional role of GABA(B) receptors within the habenula in stress resilience and vulnerability by using chronic social defeat stress (CSDS) model in C57BL/6 male mice. Approximately 47.1% of mice exhibited depression- or anxiety-like behaviors after exposure to CSDS. The vulnerable mice presented elevated c-Fos expression in the LHb when confronted with an attacker. On the other hand, the expression of GABA(B) receptors, including both GABA(B1) and GABA(B2) subunits, was significantly down-regulated in the LHb of the susceptible mice. Finally, we found the stress-induced social withdrawal symptoms could be rapidly relieved by intra-LHb injection of both baclofen and CGP36216 (a GABA(B) receptor agonist and antagonist respectively). The above results indicated that GABA(B) receptors in the LHb may play an important role in stress resilience and vulnerability, and thus, may be an important therapeutic target for treatments of stress-induced psychiatric disorders.
Asunto(s)
Habénula , Animales , Ansiedad/etiología , Habénula/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Receptores de GABA-B/metabolismo , Ácido gamma-AminobutíricoRESUMEN
Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the progressive decline of memory and cognitive function. The disease is characterized by the presence of amyloid plaques, tau tangles, altered inflammatory signaling, and alterations in numerous neurotransmitter signaling systems, including γ-aminobutyric acid (GABA). Given the extensive role of GABA in regulating neuronal activity, a careful investigation of GABA-related changes is needed. Further, given persistent inflammation has been demonstrated to drive AD pathology, the presence of GABA B receptor expressed on glia that serve a role regulation of the immune response adds to potential implications of altered GABA in AD. There has not previously been a systematic evaluation of GABA-related changes in an amyloid model of AD that specifically focuses on examining changes in GABA B receptors. In the present study, we examined alterations in several GABA-specific targets in the APP/PS1 mouse model at different ages. In the 4-month-old cohort, no significant deficits in spatial learning and memory or alterations in any of the GABAergic targets were observed compared with wild-type controls. However, we identified significant alterations in several GABA-related targets in the 6-month-old cohort that exhibited spatial learning deficits that include changes in glutamic acid decarboxylase 65, GABA transporter type 3, and GABA B receptors protein and mRNA levels. This was the same cohort at which learning and memory deficits and significant amyloid pathology was observed. Overall, our study provides evidence of altered GABAergic signaling in an amyloid model of AD at a time point consistent with AD-related deficits.
Asunto(s)
Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Receptores de GABA-B/metabolismo , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/psicología , Animales , Modelos Animales de Enfermedad , Ácido Glutámico/metabolismo , Memoria , Ratones Transgénicos , Neuroglía/metabolismo , Receptores de GABA-B/fisiología , Transducción de Señal/genética , Transducción de Señal/fisiología , Aprendizaje Espacial , Ácido gamma-Aminobutírico/metabolismoRESUMEN
We recently reported that hydrogen sulfide (H2S) is a possible relaxation factor in the rat bladder. However, there is no available information about the roles of central H2S in the micturition reflex, so we investigated the effects of centrally administered GYY4137 (H2S donor) and AOAA (H2S synthesis inhibitor) on the micturition reflex in urethane-anesthetized (0.8 g/kg, ip) male Wistar rats. Cystometry was performed before and after the administration of GYY4137 (3 or 10 nmol/rat, icv) or AOAA (30 or 100 µg/rat, icv). In some rats, SR95531 (GABAA receptor antagonist, 0.1 nmol/rat, icv) or SCH50911 (GABAB receptor antagonist, 0.1 nmol/rat, icv) was administered 30 min before GYY4137 administration (10 nmol/rat, icv). Centrally administered GYY4137 dose-dependently prolonged the intercontraction intervals (ICI) without altering maximum voiding pressure (MVP). On the other hand, centrally administered AOAA dose-dependently shortened ICI without altering MVP. The AOAA (30 µg/rat, icv)-induced ICI shortening was reversed in the central presence of GYY4137 (10 nmol/rat, icv). Centrally pretreated SR95531 or SCH50911 significantly attenuated the GYY4137 (10 nmol/rat, icv)-induced prolongation of ICI, respectively. These findings suggest that endogenous brain H2S can inhibit the rat micturition reflex via both GABAA and GABAB receptors in the brain.
Asunto(s)
Encéfalo/metabolismo , Sulfuro de Hidrógeno/metabolismo , Receptores de GABA/metabolismo , Reflejo/efectos de los fármacos , Micción/efectos de los fármacos , Ácido Aminooxiacético/farmacología , Animales , Masculino , Morfolinas/farmacología , Contracción Muscular/fisiología , Compuestos Organotiofosforados/farmacología , Ratas Wistar , Vejiga Urinaria/fisiologíaRESUMEN
The GABA analog phenibut (ß-Phenyl-GABA) is a GABAB receptor agonist that has been licensed for various uses in Russia. Phenibut is also available as a dietary supplement from online vendors worldwide, and previous studies have indicated that phenibut overdose results in intoxication, withdrawal symptoms, and addiction. F-phenibut (ß-(4-Fluorophenyl)-GABA), a derivative of phenibut, has not been approved for clinical use. However, it is also available as a nootropic supplement from online suppliers. F-phenibut binds to GABAB with a higher affinity than phenibut; therefore, F-phenibut may lead to more serious intoxication than phenibut. However, the mechanisms by which F-phenibut acts on GABAB receptors and influences neuronal function remain unknown. In the present study, we compared the potency of F-phenibut, phenibut, and the GABAB agonist (±)-baclofen (baclofen) using in vitro patch-clamp recordings obtained from mouse cerebellar Purkinje cells slice preparations Our findings indicate that F-phenibut acted as a potent GABAB agonist. EC50 of outward current density evoked by the three GABAB agonists decreased in the following order: phenibut (1362 µM) > F-phenibut (23.3 µM) > baclofen (6.0 µM). The outward current induced by GABAB agonists was an outward-rectifying K+ current, in contrast to the previous finding that GABAB agonists activates an inward-rectifying K+ current. The K+ current recorded in the present study was insensitive to extracellular Ba2+, intra- or extracellular Cs+, and intra- or extracellular tetraethylammonium-Cl. Moreover, F-phenibut suppressed action potential generation in Purkinje cells. Thus, abuse of F-phenibut may lead to severe damage by inhibiting the excitability of GABAB-expressing neurons.
Asunto(s)
Agonistas de Receptores GABA-B/farmacología , Canales de Potasio/metabolismo , Potasio/metabolismo , Células de Purkinje/efectos de los fármacos , Receptores de GABA-B/efectos de los fármacos , Ácido gamma-Aminobutírico/farmacología , Potenciales de Acción , Animales , Baclofeno/farmacología , Relación Dosis-Respuesta a Droga , Femenino , Agonistas de Receptores GABA-B/toxicidad , Técnicas In Vitro , Masculino , Ratones Endogámicos ICR , Células de Purkinje/metabolismo , Receptores de GABA-B/metabolismo , Ácido gamma-Aminobutírico/análogos & derivados , Ácido gamma-Aminobutírico/toxicidadRESUMEN
Differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLs) is a key event for axonal myelination in the central nervous system (CNS). Several growth factors and neurotransmitters like GABA are postulated as important regulators of that process, and different protein kinases may also participate in OL differentiation and myelination. However, the molecular mechanisms underlying the regulation of myelination by neurotransmitters are only partially known. In the present study, we provide evidence showing that GABA receptors (GABARs) play an important role in OL differentiation. First, we observed that OPCs and OLs synthesize GABA and expressed GABAR and transporters, both in vitro and in vivo and, in contrast to GABAARs, the subunits GABAB1R and GABAB2R are expressed in OLs over time. Then, we found that exogenous GABA increases the number of myelin segments and MBP expression in DRG-OPC cocultures, indicating that GABA regulates myelination when OLs are in contact with axons. Notably, in purified rat OPC cultures, chronic treatment with GABA and baclofen, specific GABABR agonist, accelerates OPC differentiation by enhancing the processes branching and myelin protein expression, effects that are reverted in presence of GABABR specific antagonist CGP55845. Exposure of OPCs to baclofen promotes the Src-phosphorylation, and the baclofen-induced maturation is attenuated in presence of the Src-family kinases inhibitor PP2. None of these effects are mediated by the GABAAR agonist muscimol. Together, these results highlight the relevance of the GABAergic system in OL differentiation, and indicate that this functional role is mediated through GABABR involving the participation of Src-family kinases. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
Asunto(s)
Oligodendroglía , Receptores de GABA-B , Animales , Diferenciación Celular , Células Cultivadas , Vaina de Mielina , Ratas , Ácido gamma-AminobutíricoRESUMEN
Hippocampus CA1 pyramidal cells receive γ-aminobutyric acid (GABA) release from multiple GABAergic interneurons. Combining optogenetic strategy and whole-cell recordings, we demonstrate that baclofen, a specific GABAB receptor agonist, depresses monosynaptic GABAA receptor-mediated transmission from parvalbumin (PV)-expressing interneuron terminals onto pyramidal cells with less efficacy than that from the unspecific GABAergic terminals. The depression from PV neuron terminals is mainly mediated by presynaptic P/N type calcium channels. The results suggest that GABAB receptors are widely expressed on GABAergic interneurons, where they exert inhibition onto pyramidal cells by GABA release with different efficacy. The data strengthen the proposal that diverse GABA neurons play different roles in modulating CA1 pyramidal cell excitability.
Asunto(s)
Neuronas GABAérgicas/metabolismo , Hipocampo/metabolismo , Receptores de GABA-B/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Animales , Baclofeno/farmacología , Canales de Calcio/metabolismo , Femenino , Agonistas del GABA/farmacología , Antagonistas de Receptores de GABA-B/farmacología , Hipocampo/citología , Interneuronas/metabolismo , Masculino , Ratones Transgénicos , Optogenética , Parvalbúminas/metabolismo , Técnicas de Placa-Clamp , Células Piramidales/metabolismoRESUMEN
The development, progression, metastasis and drug resistance of the most common human cancers are driven by cyclic adenosine monophosphate (cAMP)-signaling downstream of beta-adrenergic receptors (ß-Ars) coupled to the stimulatory G-protein Gs. Receptors coupled to the inhibitory G-protein Gi inhibit this signaling cascade by blocking the activation of the enzyme adenylyl cyclase that catalyzes the formation of cAMP and function as the physiological inhibitors of this signaling cascade. Members of the Gi-coupled receptor family widely expressed in the mammalian organism are GABA B receptors (GABAB-Rs) for the inhibitory neurotransmitter γ-aminobutyric acid (GABA), opioid receptors for endogenous opioid peptides and cannabinoid receptors for endogenous cannabinoids. This review summarizes current evidence for the concept that the activation of Gi-receptor signaling by pharmacological and psychological means is a promising tool for the long-term management of cAMP-driven cancers with special emphasis on the inhibitory effects of opioids on lung adenocarcinoma and its stem cells.
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Adenocarcinoma del Pulmón/tratamiento farmacológico , AMP Cíclico/farmacología , Subunidades alfa de la Proteína de Unión al GTP Gi-Go/metabolismo , Neoplasias Pulmonares/tratamiento farmacológico , Receptores Acoplados a Proteínas G/fisiología , Receptores Opioides/fisiología , Inhibidores de Adenilato Ciclasa , Adenilil Ciclasas/farmacología , Animales , Anticarcinógenos/farmacología , Cannabinoides/farmacología , AMP Cíclico/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gs/metabolismo , Humanos , Metadona/farmacología , Antagonistas de Narcóticos , Receptores Acoplados a Proteínas G/efectos de los fármacos , Transducción de Señal/fisiología , Células Madre/efectos de los fármacos , Células Madre/fisiologíaRESUMEN
Previous studies in our laboratory showed an interaction between the GABAergic and opioid systems involved in the analgesic effect of baclofen (BAC). Furthermore, it is known that sex differences exist regarding various pharmacological responses of morphine (MOR) and they are related to an increased sensitivity to MOR effects in males. The aims of the present study were to evaluate the possible involvement of the GABAB receptors in the antinociceptive responses induced by MOR (1, 3 and 9â¯mg/kg, s.c.) administration using both pharmacological (BAC 2â¯mg/kg, i.p.; and 2-OH-saclofen, SAC 0.3â¯mg/kg, intra cisterna magna) and genetic approaches (GABAB1 knockout mice; GABAB1 KO) in mice of both sexes. In addition, we explored the alterations in c-Fos expression of different brain areas involved in the antinociceptive effect of MOR using both approaches. The pharmacological approach showed a higher dose-dependent antinociceptive effect of MOR in male mice compared to female mice. BAC and SAC pretreatment potentiated and attenuated the antinociceptive effect of MOR, respectively, in both sexes. The genetic approach revealed a dose-dependent antinociceptive effect of MOR in the wild type mice, but not in the GABAB1 KO mice and no sex differences were observed. Additionally, BAC and SAC pretreatment and the lack of GABAB1 subunit of the GABAB receptor prevented the changes observed in c-Fos expression in the cingulate cortex and nucleus accumbens of male mice. Our results suggest that the GABAB receptors are involved in the MOR antinociceptive effect of both male and female mice.
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Analgésicos/farmacología , Morfina/farmacología , Receptores de GABA-B/genética , Receptores de GABA-B/metabolismo , Analgésicos/administración & dosificación , Animales , Baclofeno/administración & dosificación , Baclofeno/análogos & derivados , Baclofeno/farmacología , Conducta Animal/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Femenino , Agonistas de Receptores GABA-B/administración & dosificación , Agonistas de Receptores GABA-B/farmacología , Técnicas de Inactivación de Genes , Genes fos/genética , Genotipo , Giro del Cíngulo/efectos de los fármacos , Giro del Cíngulo/metabolismo , Locomoción/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Morfina/administración & dosificación , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Proteínas Proto-Oncogénicas c-fos/inmunología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Factores Sexuales , Transducción de Señal/efectos de los fármacosRESUMEN
Dopamine (D2) receptors provide autoinhibitory feedback onto dopamine neurons through well-known interactions with voltage-gated calcium channels and G protein-coupled inwardly-rectifying potassium (GIRK) channels. Here, we reveal a third major effector involved in D2R modulation of dopaminergic neurons - the sodium leak channel, NALCN. We found that activation of D2 receptors robustly inhibits isolated sodium leak currents in wild-type mice but not in NALCN conditional knockout mice. Intracellular GDP-ßS abolished the inhibition, indicating a G protein-dependent signaling mechanism. The application of dopamine reliably slowed pacemaking even when GIRK channels were pharmacologically blocked. Furthermore, while spontaneous activity was observed in nearly all dopaminergic neurons in wild-type mice, neurons from NALCN knockouts were mainly silent. Both observations demonstrate the critical importance of NALCN for pacemaking in dopaminergic neurons. Finally, we show that GABA-B receptor activation also produces inhibition of NALCN-mediated currents. Therefore, we identify NALCN as a core effector of inhibitory G protein-coupled receptors.
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Canales de Calcio Tipo N/metabolismo , Neuronas Dopaminérgicas/metabolismo , Canales de Potasio Rectificados Internamente Asociados a la Proteína G/metabolismo , Canales Iónicos/genética , Proteínas del Tejido Nervioso/genética , Receptores de Dopamina D2/metabolismo , Receptores de GABA-B/metabolismo , 6-Ciano 7-nitroquinoxalina 2,3-diona/farmacología , Animales , Canales de Calcio Tipo N/genética , Dopamina/farmacología , Neuronas Dopaminérgicas/citología , Neuronas Dopaminérgicas/efectos de los fármacos , Canales de Potasio Rectificados Internamente Asociados a la Proteína G/antagonistas & inhibidores , Canales de Potasio Rectificados Internamente Asociados a la Proteína G/genética , Expresión Génica , Guanosina Difosfato/análogos & derivados , Guanosina Difosfato/farmacología , Canales Iónicos/deficiencia , Transporte Iónico/efectos de los fármacos , Proteínas de la Membrana , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microtomía , Proteínas del Tejido Nervioso/deficiencia , Técnicas de Placa-Clamp , Picrotoxina/farmacología , Receptores de Dopamina D2/genética , Receptores de GABA-B/genética , Tionucleótidos/farmacología , Técnicas de Cultivo de Tejidos , Valina/análogos & derivados , Valina/farmacología , Área Tegmental Ventral/citología , Área Tegmental Ventral/metabolismoRESUMEN
Inhibition provided by local GABAergic interneurons (INs) activates ionotropic GABAA and metabotropic GABAB receptors (GABABRs). Despite GABABRs representing a major source of inhibition, little is known of their function in distinct IN subtypes. Here, we show that, while the archetypal dendritic-inhibitory somatostatin-expressing INs (SOM-INs) possess high levels of GABABR on their somato-dendritic surface, they fail to produce significant postsynaptic inhibitory currents. Instead, GABABRs selectively inhibit dendritic CaV1.2 (L-type) Ca2+ channels on SOM-IN dendrites, leading to reduced calcium influx and loss of long-term potentiation at excitatory input synapses onto these INs. These data provide a mechanism by which GABABRs can contribute to disinhibition and control the efficacy of extrinsic inputs to hippocampal networks.
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Región CA1 Hipocampal/metabolismo , Canales de Calcio Tipo L/metabolismo , Señalización del Calcio/fisiología , Interneuronas/metabolismo , Potenciación a Largo Plazo/fisiología , Receptores de GABA-B/metabolismo , Somatostatina/metabolismo , Animales , Región CA1 Hipocampal/citología , Dendritas/metabolismo , Neuronas GABAérgicas/citología , Neuronas GABAérgicas/metabolismo , Interneuronas/citología , Masculino , Ratas , Ratas Endogámicas WF , Sinapsis/metabolismoRESUMEN
RATIONALE: Previous studies have postulated functional links between GABA and cannabinoid systems in the hippocampus. The aim of the present study was to investigate any possible interaction between these systems in spatial change and object novelty discrimination memory consolidation in the dorsal hippocampus (CA1 region) of NMRI mice. METHODS: Assessment of the spatial change and object novelty discrimination memory function was carried out in a non-associative task. The experiment comprised mice exposure to an open field containing five objects followed by the examination of their reactivity to object displacement (spatial change) and object substitution (object novelty) after three sessions of habituation. RESULTS: Our results showed that the post-training intraperitoneal administration of the higher dose of ACPA (0.02 mg/kg) impaired both spatial change and novelty discrimination memory functions. Meanwhile, the higher dose of GABA-B receptor agonist, baclofen, impaired the spatial change memory by itself. Moreover, the post-training intra-CA1 microinjection of a subthreshold dose of baclofen increased the ACPA effect on spatial change and novelty discrimination memory at a lower and higher dose, respectively. On the other hand, the lower and higher but not mid-level doses of GABA-B receptor antagonist, phaclofen, could reverse memory deficits induced by ACPA. However, phaclofen at its mid-level dose impaired the novelty discrimination memory and whereas the higher dose impaired the spatial change memory. CONCLUSIONS: Based on our findings, GABA-B receptors in the CA1 region appear to modulate the ACPA-induced cannabinoid CB1 signaling upon spatial change and novelty discrimination memory functions.