RESUMEN
Cross-species studies have identified an evolutionarily conserved role for serotonin in flexible behavior including reversal learning. The aim of the current study was to investigate the contribution of serotonin within the orbitofrontal cortex (OFC) and medial prefrontal cortex (mPFC) to visual discrimination and reversal learning. Male Lister Hooded rats were trained to discriminate between a rewarded (A+) and a nonrewarded (B-) visual stimulus to receive sucrose rewards in touchscreen operant chambers. Serotonin was depleted using surgical infusions of 5,7-dihydroxytryptamine (5,7-DHT), either globally by intracebroventricular (i.c.v.) infusions or locally by microinfusions into the OFC or mPFC. Rats that received i.c.v. infusions of 5,7-DHT before initial training were significantly impaired during both visual discrimination and subsequent reversal learning during which the stimulus-reward contingencies were changed (A- vs. B+). Local serotonin depletion from the OFC impaired reversal learning without affecting initial discrimination. After mPFC depletion, rats were unimpaired during reversal learning but slower to respond at the stimuli during all the stages; the mPFC group was also slower to learn during discrimination than the OFC group. These findings extend our understanding of serotonin in cognitive flexibility by revealing differential effects within two subregions of the prefrontal cortex in visual discrimination and reversal learning.
Asunto(s)
Aprendizaje Discriminativo/fisiología , Corteza Prefrontal/metabolismo , Aprendizaje Inverso/fisiología , Neuronas Serotoninérgicas/metabolismo , Serotonina/metabolismo , Percepción Visual/fisiología , 5,6-Dihidroxitriptamina/administración & dosificación , 5,6-Dihidroxitriptamina/análogos & derivados , 5,6-Dihidroxitriptamina/toxicidad , Animales , Creatinina/administración & dosificación , Creatinina/análogos & derivados , Creatinina/toxicidad , Aprendizaje Discriminativo/efectos de los fármacos , Infusiones Intraventriculares , Masculino , Estimulación Luminosa/métodos , Corteza Prefrontal/efectos de los fármacos , Ratas , Aprendizaje Inverso/efectos de los fármacos , Neuronas Serotoninérgicas/efectos de los fármacos , Percepción Visual/efectos de los fármacosRESUMEN
Comparative analysis of the action of chlorpromazine (CPZ) and neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) on defensive reactions and locomotion of grape snail and elaboration of long-term sensitization (LTS), was carried out. Long-term (chronic) injection of chlorpromazine led to significant increasing of a pneumostome closing time and to changing of motor behaviour towards decrease of the velocity of the locomotion. Daily injections of 5,6-DHT in small doses within a week were accompanied by the gradual decrease of the velocity of snails locomotion, which was kept for a week. Similar effect was observed in injection of neurotoxin (30 mgs/kg). Injections of CPZ prevents elaboration of LTS, as well as injections of 5,6-DHT. After the action of CPZ, LTS, LTS followed by CPZ, and also during elaboration of LTS after injection of CPZ, the velocity of locomotion directly depended on the length of leg. During elaboration of LTS after injection of 5,6-DHT, such dependency is not retained. Electrophysiological study revealed that chronic injections of CPZ led to depolarizing shift of membrane potential and decrease of the threshold of action potential generation in command neurons as after injection of neurotoxin 5,6-DHT. Therefore, the action of neuroleptic drug CPZ on the defensive behaviour, locomotion of grape snail and electrical characteristics of identifying neurons is comparable with the action of toxic analogue of serotonin.
Asunto(s)
5,6-Dihidroxitriptamina/administración & dosificación , Clorpromazina/administración & dosificación , Antagonistas de Dopamina/administración & dosificación , Reacción de Fuga/efectos de los fármacos , Locomoción/efectos de los fármacos , Neuronas/fisiología , Serotoninérgicos/administración & dosificación , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Reacción de Fuga/fisiología , Caracoles Helix , Potenciación a Largo Plazo/efectos de los fármacos , Potenciación a Largo Plazo/fisiologíaRESUMEN
The role played by the serotoninergic system in the control of puberty onset and first ovulation in rats is studied in this paper by analyzing the effects of injecting the neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) into the dorsal (DRN) or medial (MRN) raphe nucleus of 30-day-old female rats. Complete lesion to the DRN resulted in the blockade of ovulation and a decrease in both the number of ovarian follicles and the serum concentration of follicle stimulating hormone (FSH). This treatment was also found to be associated with an increase in serotoninergic activity in the anterior and medial hypothalami. A lesion to the central portion of the DRN resulted in a significant decrease in the concentration of progesterone in serum and in the number of ova shed by ovulating animals. The lesion to the lateral portion of the DRN did not have an apparent effect on ovulation rate, the number of ova shed, nor in hormone serum concentration. The injection of propranolol to rats with a lesion to the DRN restored ovulation in 73% of treated animals and returned serotoninergic activity in the anterior hypothalamus to levels similar to those of sham-operated animals. In turn, in the medial hypothalamus, the increase in serotoninergic activity was not modified. The results presented herein suggest that serotoninergic inputs to the anterior hypothalamus have a direct influence on gonadotropin secretion and first ovulation, while the noradrenergic innervation exerts an indirect influence.
Asunto(s)
5,6-Dihidroxitriptamina/administración & dosificación , Núcleo Talámico Mediodorsal/efectos de los fármacos , Núcleos del Rafe/efectos de los fármacos , Serotoninérgicos/administración & dosificación , 5,6-Dihidroxitriptamina/farmacología , Antagonistas Adrenérgicos beta/farmacología , Animales , Mapeo Encefálico , Estradiol/sangre , Estro/efectos de los fármacos , Estro/metabolismo , Femenino , Hormona Folículo Estimulante/sangre , Ácido Hidroxiindolacético/metabolismo , Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Hormona Luteinizante/metabolismo , Núcleo Talámico Mediodorsal/fisiología , Folículo Ovárico/efectos de los fármacos , Folículo Ovárico/metabolismo , Folículo Ovárico/fisiopatología , Ovulación/efectos de los fármacos , Ovulación/metabolismo , Progesterona/sangre , Propranolol/farmacología , Núcleos del Rafe/anatomía & histología , Núcleos del Rafe/fisiología , Ratas , Ratas Endogámicas , Serotoninérgicos/farmacología , Vagina/efectos de los fármacos , Vagina/metabolismoRESUMEN
Previous studies indicated that in immature rats testicular administration of oxytocin stimulates testicular steroidogenesis. In the present study, testicular treatment with oxytocin (50 ng) was combined with pharmacological or surgical denervation of the testis in hemigonadectomized immature rats. For denervation 5,6-dihydroxytryptamine (160 micrograms/testis), a substance that destroys serotoninergic neuronal elements, was injected intratesticularly or vasectomy was performed, which also includes transection of the inferior testicular nerve. In 9-day-old animals both vasectomy and pretreatment of the testis with 5,6-dihydroxytryptamine prevented the oxytocin-induced rise in serum testosterone concentration. In addition, intratesticular injection of oxytocin combined with vasectomy resulted in a significant increase in in vitro basal testosterone secretion of the testis. A similar effect was not observed in the 5,6-dihydroxytryptamine-pretreated group receiving oxytocin. The results indicate that testicular innervation is involved in the control of local peptide effects, and data further suggest a differential role of these neural elements in intratesticular regulatory processes.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , Oxitocina/farmacología , Testículo/efectos de los fármacos , Testículo/crecimiento & desarrollo , Testosterona/biosíntesis , Vasectomía , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Desnervación , Masculino , Orquiectomía , Ratas , Ratas Sprague-Dawley , Testículo/inervaciónRESUMEN
Microinjection of the arginin-vasopressin into the medial parabrachial nucleus, n. cuneiformis, raphe median nucleus and raphe magnus nucleus suppressed spontaneous locomotor activity and orienting response to electrical stimulation of hypothalamus in rats. Microinjections of 5,6-dihydroxytriptamine in n. raphe magnus blocked the inhibition of behaviour elicited by vasopressin.
Asunto(s)
Arginina Vasopresina/administración & dosificación , Conducta Animal/efectos de los fármacos , Tronco Encefálico/efectos de los fármacos , Inhibición Neural/efectos de los fármacos , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Conducta Animal/fisiología , Tronco Encefálico/fisiología , Interacciones Farmacológicas , Estimulación Eléctrica , Electrodos Implantados , Masculino , Microinyecciones , Inhibición Neural/fisiología , Ratas , Receptores de Serotonina/efectos de los fármacos , Receptores de Serotonina/fisiologíaRESUMEN
The ambient temperature had a confounding influence on the licking response in the formalin test. No effect was demonstrated in the early phase. In the late phase, the licking activity was much lower at 20 degrees C than at 25 degrees C. Both the intensity and the duration of the response were increased by increasing the ambient temperature from 20 degrees C to 28 degrees C. 5,6-Dihydroxytryptamine lesions of descending serotonergic pathways induced an increase in the nociceptive response at an ambient temperature of 20 degrees C, while the response was no different from control values at 25 degrees C. Differences in paw skin temperature may explain these temperature dependent effects. It was concluded that control of the ambient temperature is necessary to obtain reliable results in the formalin test, late phase.
Asunto(s)
Conducta Animal/fisiología , Nociceptores/fisiología , Dimensión del Dolor , Temperatura , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Inyecciones Espinales , Masculino , Ratones , Receptores de Serotonina/fisiología , Temperatura Cutánea/fisiologíaAsunto(s)
5,6-Dihidroxitriptamina/farmacología , Electroacupuntura , Núcleos del Rafe/fisiología , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Electrofisiología , Inyecciones Intraventriculares , Masculino , Neuronas/fisiología , Nociceptores/fisiología , Ratas , Serotonina/metabolismo , Médula Espinal/fisiologíaRESUMEN
The localization of serotonin-immunoreactivity (5-HT-IR) in the locus ceruleus (LC) of rats was studied by the peroxidase-anti-peroxidase method using a purified antibody obtained from a rabbit. Antibody production was performed according to the method of Grota and Brown (1974). The antibody was applied to serial cryostat sections with alternate counterstaining by cresyl violet, after intraventricular injections of 5,6-dihydroxytryptamine or 5,7-dihydroxytryptamine prior to treatment with pargyline and a precursor of 5-HT. The majority of LC neurons were immunopositive, and more than half of all LC neurons clearly showed 5-HT-IR. Although core cells were the most predominant, all types of neurons were immunopositive, and randomly scattered throughout the LC. The uptake inhibitor, Lilly 110140, administered in sufficient amounts prior to an injection of pargyline, did not reduce 5-HT-IR within the LC. The results suggest that LC neurons receive 5-hydroxytryptophan (5-HTP) through an afferent vascular-neuronal channel and/or by diffusion from blood capillaries much more than 5-HT itself. We consider from these results that all types of LC neurons throughout the nucleus are masked 5-HT cells, and that the majority of LC neurons utilize blood-borne 5-HTP as an immediate precursor for intraneuronal 5-HT synthesis.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , 5,7-Dihidroxitriptamina/farmacología , Locus Coeruleus/anatomía & histología , Serotonina/metabolismo , 5,6-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/administración & dosificación , Animales , Anticuerpos/aislamiento & purificación , Formación de Anticuerpos/efectos de los fármacos , Especificidad de Anticuerpos , Cromatografía de Afinidad , Reacciones Cruzadas , Femenino , Fluoxetina/farmacología , Immunoblotting , Técnicas para Inmunoenzimas , Inyecciones Intraventriculares , Locus Coeruleus/inmunología , Locus Coeruleus/metabolismo , Pargilina/farmacología , Ratas , Ratas Endogámicas , Serotonina/biosíntesis , Serotonina/inmunologíaRESUMEN
We examined in mice whether tail skin temperatures and tail-flick reflexes were changed after spinal transection or intrathecal (i.th.) injection of the serotonin (5-HT) neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) or the 5-HT receptor antagonist metergoline. Transection of the spinal cord reduced tail-flick latency (the time needed to evoke the tail-flick reflex by radiant heat) and increased tail skin temperature 15-21 days after surgery. Analysis of covariance showed that the effect of tail skin temperature on tail-flick latency was far more pronounced than the effect of spinal transection. Intrathecal injection of 5,6-DHT (5 or 10 micrograms mouse-1), which extensively reduced the spinal levels of 5-HT, reduced tail-flick latency and increased tail skin temperature 1-5 days after treatment. Similarly, tail-flick latency was shortened and tail skin temperature elevated 15 min after i.th. injection of metergoline (0.5 micrograms mouse-1). Analysis of covariance showed no significant effect of i.th. 5,6-DHT or i.th. metergoline on tail-flick latency. Tail skin temperature, on the other hand, had a highly significant effect on tail-flick latency. The results show that the facilitation of the tail-flick reflex in spinally transected mice and mice injected i.th. with 5,6-DHT or metergoline is mainly caused by increased tail skin temperature. The data do not indicate that descending 5-HT pathways tonically inhibit the tail-flick reflex.
Asunto(s)
Receptores de Serotonina/fisiología , Reflejo/fisiología , Temperatura Cutánea , Médula Espinal/fisiología , Transmisión Sináptica , Cola (estructura animal)/fisiología , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Inyecciones Espinales , Masculino , Metergolina/administración & dosificación , Ratones , Ratones Endogámicos , Nociceptores/fisiología , Receptores de Serotonina/efectos de los fármacos , Serotonina/administración & dosificación , Temperatura Cutánea/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Cola (estructura animal)/inervaciónRESUMEN
Levels of 24 free amino acids were estimated in the brain after administration of 5,6-dihydroxytryptamine and 6-hydroxydopamine into the lateral brain ventricles of male Wistar rats. These neurotransmitters caused serotoninectomy and sympathectomy in the diencephalon, striatum, brain stem and medulla, thalamus and hypothalamus, cerebral cortex and cerebellum. The most abundant amino acids in these brain structures were: glutamic acid, serine, aspartic acid, cystine, gamma-aminobutyric acid, glycine, tryptophan and alanine. We detected and quantified changes in the levels of these and other amino acids in the investigated regions of the rat central nervous system, under the influence of these two neurotransmitters.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , Aminoácidos/metabolismo , Encéfalo/metabolismo , Ventrículos Cerebrales/metabolismo , Hidroxidopaminas/farmacología , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Encéfalo/efectos de los fármacos , Ventrículos Cerebrales/efectos de los fármacos , Citosol/efectos de los fármacos , Citosol/metabolismo , Hidroxidopaminas/administración & dosificación , Inyecciones Intraventriculares , Masculino , Especificidad de Órganos , Oxidopamina , Ratas , Ratas EndogámicasRESUMEN
Methamphetamine (MA) in high doses produces long-term toxic effects on the serotonergic system in the rat brain, including depletions of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid and reductions in 5-HT reuptake and tryptophan hydroxylase activity. In this study, the formation of 5,6-dihydroxytryptamine (5,6-DHT), a serotonergic neurotoxin, was observed in the rat hippocampus after a single 100 mg/kg injection of MA. The 5,6-DHT was detected by reverse-phase high-performance liquid chromatography with electrochemical detection in tissue samples taken 0.5-4 h after MA administration; the highest levels of 5,6-DHT (0.032 ng/mg wet tissue) were detected at 1 h. Following administration of MA, 5-HT was also depleted in the neocortex, but 5,6-DHT was not detected as frequently in this brain region as in the hippocampus. Comparisons were made between the long-term hippocampal 5-HT depletions seen either after an injection of MA or after intraventricular 5,6-DHT infusions and the levels of 5,6-DHT measured in the hippocampus shortly after each treatment. The amount of 5,6-DHT produced after MA administration appears to be adequate to cause the observed long-term 5-HT depletions. We suggest that 5,6-DHT formed from 5-HT may mediate the neurotoxic effects of MA on serotonergic nerve terminals.
Asunto(s)
5,6-Dihidroxitriptamina/biosíntesis , Encéfalo/metabolismo , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Ácido Hidroxiindolacético/metabolismo , Inyecciones Subcutáneas , Masculino , Metanfetamina/farmacología , Ratas , Ratas Endogámicas , Serotonina/metabolismo , Factores de TiempoRESUMEN
The 5,6-dihydroxytryptamine-induced lesions of serotonergic neurons in the dorsal raphe nucleus of the cat resulted in an increase in the carbachol-induced growling response, a decrease in the concentrations of noradrenaline, serotonin and 5-hydroxyindoleacetic acid in the hypothalamus, midbrain and amygdala, and an increase in the hypothalamic dopamine level. Those changes were observed 6, but not 23, days after the lesion. The results suggest a close correlation between the state of the emotional-defensive arousal and neurochemical changes in the "emotional regions" of the brain. The role of the reduced activity of the serotonergic system in augmenting the emotional-defensive behavior was discussed.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , Agresión/efectos de los fármacos , Aminas Biogénicas/metabolismo , Química Encefálica/efectos de los fármacos , Carbacol/farmacología , Núcleos del Rafe/fisiología , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Gatos , Dopamina/metabolismo , Femenino , Ácido Hidroxiindolacético/metabolismo , Inyecciones , Masculino , Norepinefrina/metabolismo , Serotonina/metabolismoRESUMEN
Microinjection of the dopamine receptor agonist apomorphine, and to a lesser extent dopamine itself, into the nucleus raphe magnus increased tail flick latency in conscious rats. The hypoalgesia was dependent on the integrity of catecholamine-containing pathways originating near the third ventricle and was diminished by systemic depletion of hydroxytryptamine. No simple neuronal circuitry could explain all the effects observed.
Asunto(s)
Apomorfina/farmacología , Dopamina/farmacología , Nociceptores/efectos de los fármacos , Núcleos del Rafe , 5,6-Dihidroxitriptamina/administración & dosificación , 5,6-Dihidroxitriptamina/farmacología , Animales , Apomorfina/administración & dosificación , Ventrículos Cerebrales/efectos de los fármacos , Dopamina/administración & dosificación , Hidroxidopaminas/administración & dosificación , Hidroxidopaminas/farmacología , Masculino , Microinyecciones , Oxidopamina , Sustancia Gris Periacueductal/efectos de los fármacos , Fenilalanina/administración & dosificación , Fenilalanina/farmacología , RatasRESUMEN
Quantitative evaluation of spermatogenesis at stage VII of the cycle of the seminiferous epithelium and radioimmunoassay of plasma testosterone were performed in adult Wistar rats after intraventricular injection of 5,6-dihydroxytryptamine (5,6-DHT). The rats were killed 2, 10 and 21 days after injection. Brain 5-hydroxytryptamine (5-HT) and plasma testosterone levels were found to be significantly lower in all rats treated with 5,6-DHT. A significant reduction in step 7 spermatid count was also observed after 10 and 21 days. Supplementation with human chorionic gonadotrophin for 21 days in rats injected with 5,6-DHT partially prevented the step 7 spermatid degeneration and increased testosterone levels without producing any effect on brain concentrations of 5-HT. These results suggest that changes in testicular steroidogenesis and spermatogenesis are secondary to pituitary gonadotrophin release which, in turn, is under the influence of brain 5-HT neurones.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , Espermatogénesis/efectos de los fármacos , Testosterona/sangre , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Química Encefálica , Recuento de Células , Inyecciones Intraventriculares , Masculino , Ratas , Ratas Endogámicas , Epitelio Seminífero/efectos de los fármacos , Serotonina/análisis , Espermátides/efectos de los fármacos , Factores de TiempoRESUMEN
The effect of two potent neurotoxic agents for 5HT neurons, 5,6-DHT and 5,7-DHT, intraventricularly injected, has been studied on the values and rhythm of plasmatic corticosterone secretion in the male Wistar rat model, along an entire day: 4 a.m., 8 a.m., noon, 5 p.m. and midnight. The dose administered for each drug was 100 micrograms/animal in a single injection. The levels of corticosterone were determined 15 and 30 days post-injection. The effects observed for both drugs were similar at similar times: highly significant decreases in all the studied points which fall under the same line of secretion and evince an absolute inhibition of the cyclic rhythm. There are no significant differences among the values obtained with different drugs at various times. The contents of NA and 5HT significantly decrease for both drugs especially those of the 5HT on the 15th day. 30 days after the injection there is a small recovery of 5HT, but differences with control values are still significant. On the other hand the recovery of NA was almost total (near 100%). The results are discussed within the highly controversial frame of the influence of central 5HT neurons on the various types of secretion of the hypothalamic-pituitary-adrenal axis. The data obtained with this "chronic model" are confronted with those from other authors who have used drugs with transitory effect on the 5HT brain metabolism.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , 5,7-Dihidroxitriptamina/farmacología , Corticosterona/metabolismo , Dihidroxitriptaminas/farmacología , Sistema Hipotálamo-Hipofisario/efectos de los fármacos , Sistema Hipófiso-Suprarrenal/efectos de los fármacos , 5,6-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/administración & dosificación , Corteza Suprarrenal/metabolismo , Animales , Ritmo Circadiano , Inyecciones Intraventriculares , Masculino , Ratas , Ratas EndogámicasRESUMEN
The taste buds on the barbels in three species of teleosts (Cyprinus carpio, Misgurnus anguillicaudatus, Parasilurus asotus) were studied by means of fluorescence- and electron microscopy. Intensely yellow-fluorescent cells, which are disk-shaped and located exclusively in a basal position, are observed in the barbel-buds of all fishes examined. The basal cells contain a large number of small clear vesicles approximately 40-60 nm in diameter, which show a tendency to aggregate in the cytoplasm facing the junction of the nerve terminals; chemically transmitting synapses are seen in the latter region. It is suggested from the present observations that the basal cells in the barbel-bud may originate from Schwann cells and have a dual function both as mechanoreceptors and paracrine elements. Since the administration of 5,6-DHT results in an appearance of small dense vesicles among the small clear vesicles, the possibility exists that the basal cell may be capable of taking up monoamines and storing them in the small clear vesicles.
Asunto(s)
Peces/anatomía & histología , Papilas Gustativas/citología , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Carpas/anatomía & histología , Microscopía Fluorescente , Nialamida/administración & dosificación , Papilas Gustativas/ultraestructuraRESUMEN
Intrathecal administration of 5,6-dihydroxytryptamine (5,6-DHT) (5 micrograms) to mice selectively lesioned descending serotonergic pathways, reducing spinal levels of 5-hydroxytryptamine (5-HT) by 80%, without significantly changing the levels of noradrenaline. Increased sensitivity to noxious stimulation, as measured by the tail-flick and hot-plate tests, was observed 2 days after injection of 5,6-DHT. The tail-flick latencies returned to normal on day 6, but were again reduced by administration of the 5-HT receptor blocker metergoline, suggesting that the normalization process involved compensatory mechanisms in the remaining 5-HT system. In the hot-plate test, the latencies both to shaking or kicking of a hindpaw (kick) and to hindpaw lick were recorded, but the time course for the changes of these two responses was found to be different. The latencies to hindpaw lick were normalized within 2 weeks, whereas the hindpaw kick latencies remained reduced throughout the 21 day observation period.
Asunto(s)
5,6-Dihidroxitriptamina/farmacología , Nociceptores/efectos de los fármacos , 5,6-Dihidroxitriptamina/administración & dosificación , Animales , Conducta Animal/efectos de los fármacos , Inyecciones Espinales , Masculino , Ratones , Tiempo de Reacción/efectos de los fármacos , Serotonina/metabolismo , Médula Espinal/metabolismoRESUMEN
Local injection of 5,7-dihydroxytryptamine into the median raphe nucleus of rats pretreated with desipramine decreases the serotonin content of the hippocampus and cortex. The turnover of acetylcholine, as measured by the rate of decline of acetylcholine content after hemicholinium-3, is not affected in the hippocampus or the striatum, but is increased in the cortex by such treatment. Local injection of 5,7-dihydroxytryptamine into the dorsal raphe nucleus of desipramine-treated rats decreases the serotonin content of the hippocampus, cortex, and striatum. The turnover of acetylcholine is increased in the hippocampus and cortex, but not affected in the striatum. Thus, serotonergic neurons from the median raphe nucleus appear to tonically inhibit cholinergic neurons in the cortex, and serotonergic neurons from the dorsal raphe nucleus appear to tonically inhibit cholinergic neurons in the hippocampus and cortex. These serotonergic neurons do not appear to act tonically on striatal cholinergic neurons.