RESUMEN
Light intensity plays an important role in the regulation of growth, behavior, reproduction, and welfare of avian species. Light intensity preference behavior has been suggested to be involved in welfare of birds. This study aims to investigate the effects of different light intensity and dual light intensity choice (DLIC) lighting program on plasma corticosterone (CORT), and tryptophan hydroxylase 2 (TPH2, the rate-limiting enzyme of serotonin biosynthesis) and tyrosine hydroxylase (TH, the rate-limiting enzyme of dopamine biosynthesis) gene expression in the brainstem of male chickens. Day old broilers were housed in two commercial houses, and placed in 24 pens. All the treatment groups were provided with 23â¯h light (L) /1â¯h dark (D) and 30â¯lx (lx) light intensity during the first week and then 18L:6D (10â¯lx) from day 7 to 14. Blood and brain were sampled at 14â¯days of age (10â¯lx) before the onset of light treatments. On day 15, four treatments (2, 10, 20, and 100â¯lx), and DLIC treatment (2/20â¯lx) were initiated. Samples were collected on days 15, 16, 17, 30 and 41. TPH2 expression in the dorsal raphe nucleus (DRN) and caudal raphe nucleus (CRN) of brainstem, and TPH2 and TH expression in ventral tegmental areas (VTN) of the midbrain were determined by qPCR. Results showed that bright light and DLIC lighting program temporarily attenuated plasma CORT, suggesting the short-term stress attenuating effect of bright light and DLIC lighting program. Differential TPH2 expression in the DRN and CRN observed in the DLIC birds indicate a significant effect of DLIC lighting program on the serotonergic activity in the avian brainstem. At the 41â¯days of age, the significant downregulation of TPH2 and TH expression occurred in the VTA of DLIC treated birds compared to the other group of birds. Taken together, temporal and spatial regulation of TPH2 and TH expression by DLIC lighting program indicate that compensatory regulation of serotonergic and dopaminergic activities might be involved in the light intensity preference behavior of birds, suggesting a possible beneficial effect of the DLIC lighting program on broiler welfare.
Asunto(s)
Pollos/sangre , Pollos/metabolismo , Corticosterona/sangre , Dopamina/metabolismo , Luz , Serotonina/metabolismo , Animales , Tronco Encefálico/metabolismo , Tronco Encefálico/efectos de la radiación , Pollos/crecimiento & desarrollo , Regulación Enzimológica de la Expresión Génica/efectos de la radiación , Masculino , Núcleos del Rafe/metabolismo , Núcleos del Rafe/efectos de la radiación , Triptófano Hidroxilasa/genética , Triptófano Hidroxilasa/metabolismo , Tirosina 3-Monooxigenasa/genética , Tirosina 3-Monooxigenasa/metabolismo , Área Tegmental Ventral/metabolismoRESUMEN
The aim of this study was to investigate the effect of continuous extremely low frequency magnetic fields (ELF-MFs) with a frequency of 10 Hz and an intensity of 690-720 µT on the level of 5-hydroxyindolacetic acid (5-HIAA) in adult male Wistar rats. A total of 24 adult Wistar male rats were used, and after exposure with an ELF-MF for 15 successive days, all rats in each test were anesthetized with chloral hydrate. Then, they were placed in a stereotaxic frame for surgery and a microdialysis process. Dialysate samples were analyzed to measure the amount of 5-HIAA by high performance liquid chromatography (HPLC) using electrochemical detection. Results showed that ELF-MF exposure for 15 days, 1 h daily, was not effective in altering the level of 5-HIAA. However, ELF-MF exposure for 15 days, 3 h daily, decreased the level of the 5-HIAA in the raphe nucleus. It can be concluded that ELF-MFs affect the serotonergic system and may be used to treat nervous system diseases. This study is an initial step towards helping cure depression using ELF-MFs.
Asunto(s)
Ácido Hidroxiindolacético/metabolismo , Campos Magnéticos , Núcleos del Rafe/metabolismo , Núcleos del Rafe/efectos de la radiación , Animales , Cromatografía Líquida de Alta Presión , Masculino , Metaboloma/efectos de la radiación , Ratas Wistar , Estándares de Referencia , Serotonina/metabolismoRESUMEN
Serotonin 2c receptors (5-HT2c-Rs) are drug targets for certain mental disorders, including schizophrenia, depression, and anxiety. 5-HT2c-Rs are expressed throughout the brain, making it difficult to link behavioral changes to circuit specific receptor expression. Various 5-HT-Rs, including 5-HT2c-Rs, are found in the dorsal raphe nucleus (DRN); however, the function of 5-HT2c-Rs and their influence on the serotonergic signals mediating mood disorders remain unclear. To investigate the role of 5-HT2c-Rs in the DRN in mice, we developed a melanopsin-based optogenetic probe for activation of Gq signals in cellular domains, where 5-HT2c-Rs are localized. Our results demonstrate that precise temporal control of Gq signals in 5-HT2c-R domains in GABAergic neurons upstream of 5-HT neurons provides negative feedback regulation of serotonergic firing to modulate anxiety-like behavior in mice.
Asunto(s)
Ansiedad/fisiopatología , Retroalimentación Fisiológica , Neuronas GABAérgicas/metabolismo , Subunidades alfa de la Proteína de Unión al GTP Gq-G11/metabolismo , Inhibición Neural , Receptor de Serotonina 5-HT2C/metabolismo , Serotonina/metabolismo , Potenciales de Acción/efectos de la radiación , Animales , Ansiedad/metabolismo , Ansiedad/patología , Calcio/metabolismo , Regulación hacia Abajo/efectos de la radiación , Retroalimentación Fisiológica/efectos de la radiación , Neuronas GABAérgicas/patología , Neuronas GABAérgicas/efectos de la radiación , Células HEK293 , Humanos , Espacio Intracelular/metabolismo , Espacio Intracelular/efectos de la radiación , Luz , Ratones , Inhibición Neural/efectos de la radiación , Optogenética , Estructura Terciaria de Proteína , Núcleos del Rafe/metabolismo , Núcleos del Rafe/efectos de la radiación , Opsinas de Bastones/química , Opsinas de Bastones/metabolismo , Transducción de Señal/efectos de la radiaciónRESUMEN
BACKGROUND: The dorsal raphe nucleus (DRN) of the mesencephalon is a complex multi-functional and multi-transmitter nucleus involved in a wide range of behavioral and physiological processes. The DRN receives a direct input from the retina. However little is known regarding the type of retinal ganglion cell (RGC) that innervates the DRN. We examined morphological characteristics and physiological properties of these DRN projecting ganglion cells. METHODOLOGY/PRINCIPAL FINDINGS: The Mongolian gerbils are highly visual rodents with a diurnal/crepuscular activity rhythm. It has been widely used as experimental animals of various studies including seasonal affective disorders and depression. Young adult gerbils were used in the present study. DRN-projecting RGCs were identified following retrograde tracer injection into the DRN, characterized physiologically by extracellular recording and morphologically after intracellular filling. The result shows that DRN-projecting RGCs exhibit morphological characteristics typical of alpha RGCs and physiological response properties of Y-cells. Melanopsin was not detected in these RGCs and they show no evidence of intrinsic photosensitivity. CONCLUSIONS/SIGNIFICANCE: These findings suggest that RGCs with alpha-like morphology and Y-like physiology appear to perform a non-imaging forming function and thus may participate in the modulation of DRN activity which includes regulation of sleep and mood.
Asunto(s)
Forma de la Célula , Núcleos del Rafe/citología , Células Ganglionares de la Retina/citología , Animales , Forma de la Célula/efectos de la radiación , Dendritas/metabolismo , Femenino , Gerbillinae , Espacio Intracelular/metabolismo , Espacio Intracelular/efectos de la radiación , Luz , Núcleos del Rafe/fisiología , Núcleos del Rafe/efectos de la radiación , Células Ganglionares de la Retina/efectos de la radiación , Percepción Visual/efectos de la radiaciónRESUMEN
Several available reports demonstrate the presence of infraslow activity (<0.5 Hz) in structures of the auditory system of the brain. It was reported earlier that specific alterations of this activity in the domain of seconds (0.1-0.5 Hz) occurred in the medial geniculate nucleus (MGN) and primary auditory cortex (A1) in response to acoustic stimuli. The present study was performed to test two hypotheses: (1) that potentials in the domain of seconds (0.1-0.5 Hz) reflect specific and direct interactions of the MGN and A1 during neural processing of sensory information, and (2) that low-frequency infraslow potentials in the A1 (<0.1 Hz) are related to brainstem influences originating from the locus coeruleus (LC) and dorsal raphe nucleus (DRN). The experimental subjects were 25 adult rats with chronic stereotaxic electrodes implanted in the MGN, A1, LC, and DRN. The animals were anesthetized and infraslow activity was once recorded under several experimental conditions: (1) in the A1 before and after electrical stimulation of MGN, (2) in the A1 before and after electrical stimulation of LC, and (3) in the A1 before and after electrical stimulation of DRN. The effects of MGN stimulation were limited to overall increases in spectral power in the frequency domain of 0.1-0.5 Hz. Specifically, power increased in the frequencies of 0.1-0.25, 0.35-0.4, and 0.45-0.5 Hz in the A1 after MGN stimulation. The electrical stimulation of either the LC or DRN affected only multisecond activity (0.0167-0.04 Hz) in the A1 in the similar way (increase of powers of multisecond potentials), but it does not induced any changes in the activity with the frequencies of 0.1-0.5 Hz in this structure. These results support tentative conclusions that infraslow activity in the range of 0.1-0.5 Hz is implicated in specific mechanisms of interactions within the MGN-A1 thalamic-cortical system, whereas multisecond potentials (0.0167-0.04 Hz) in A1 are mainly attributed to the influences of brainstem nuclei (like LC and DRN) on general neuronal excitability of this auditory cortical area.
Asunto(s)
Corteza Auditiva/fisiología , Potenciales Evocados Auditivos/fisiología , Cuerpos Geniculados/fisiología , Locus Coeruleus/fisiología , Núcleos del Rafe/fisiología , Estimulación Acústica/métodos , Análisis de Varianza , Animales , Vías Auditivas/fisiología , Estimulación Eléctrica/métodos , Cuerpos Geniculados/efectos de la radiación , Locus Coeruleus/efectos de la radiación , Masculino , Núcleos del Rafe/efectos de la radiación , RatasRESUMEN
Evidence has accumulated suggesting that the median raphe (MR) mediates hippocampal theta desynchronization. However, few studies have evaluated theta-related neural circuitry during MR manipulation. In urethane-anesthetized rats, we investigated the effects of MR stimulation on hippocampal field and cell activity using high-frequency (100 Hz), theta burst (TBS), and slow-frequency electrical stimulation (0.5 Hz). We demonstrated that high-frequency stimulation of the MR did not elicit deactivated patterns in the forebrain, but rather elicited low-voltage activity in the neocortex and small-amplitude irregular activity (SIA) in the hippocampus. Both hippocampal phasic theta-on and -off cells were inhibited by high-frequency MR stimulation, although MR stimulation failed to affect cells that had neither state or phase relationships with theta field activity. TBS of the MR-induced theta field activity phase locked to the stimulation. Slow-frequency stimulation elicited a state-dependent reset of theta phase through a short-latency inhibition (5 ms) in phasic theta-on cells. Subpopulations of phasic theta-on cells responded in either oscillatory or nonoscillatory patterns to MR pulses, depending on their intraburst interval. off cells exhibited a state-dependent modulation of cell firing occurring preferentially during nontheta. The magnitude of MR-induced reset varied as a function of the phase of the theta oscillation when the pulse was administered. Therefore high-frequency stimulation of the MR appears to disrupt hippocampal theta through a state-dependent, short-latency inhibition of rhythmic cell populations in the hippocampus functioning to switch theta oscillations to an activated SIA field state.
Asunto(s)
Estimulación Eléctrica , Hipocampo/fisiología , Red Nerviosa/fisiología , Inhibición Neural/fisiología , Núcleos del Rafe/efectos de la radiación , Ritmo Teta , Animales , Relación Dosis-Respuesta en la Radiación , Análisis de Fourier , Hipocampo/citología , Masculino , Neocórtex/fisiología , Red Nerviosa/efectos de la radiación , Inhibición Neural/efectos de la radiación , Neuronas/clasificación , Neuronas/fisiología , Neuronas/efectos de la radiación , Núcleos del Rafe/fisiología , Ratas , Ratas Long-EvansRESUMEN
The authors hypothesized that repeated rewarding electrical stimulation of the dorsal raphe can produce behavioral sensitization to psychostimulants. Groups of male rats were implanted with a stimulation electrode and preexposed to brain stimulation at parameters set to equate rewarding effectiveness across rats. Control groups were implanted with an electrode but never stimulated, or not implanted at all. Twenty-four hours after the 12th self-stimulation session, all groups were challenged with amphetamine (0.5 mg/kg, ip), nicotine (0.2 mg/kg, sc), or saline, and locomotor activity was measured for 1 hr. Locomotor responses to amphetamine and to nicotine were significantly greater in rats preexposed to brain stimulation. These findings suggest at least partial overlap of underlying substrates. ((c) 2007 APA, all rights reserved).
Asunto(s)
Estimulación Eléctrica/métodos , Actividad Motora/efectos de los fármacos , Actividad Motora/efectos de la radiación , Psicotrópicos/farmacología , Núcleos del Rafe/efectos de la radiación , Anfetamina/farmacología , Análisis de Varianza , Animales , Conducta Animal , Relación Dosis-Respuesta en la Radiación , Conducta Exploratoria/efectos de los fármacos , Conducta Exploratoria/efectos de la radiación , Masculino , Nicotina/farmacología , Ratas , Ratas Sprague-Dawley , AutoestimulaciónRESUMEN
Electrophysiological studies combined with local neurotoxic lesions were conducted on anaesthetized rats in order to determine whether the dorsal raphe nucleus (DRN) inhibits the intergeniculate leaflet (IGL) of the lateral geniculate nucleus by means of innervation by serotonin-containing fibres. In the control animals, electrical stimulation of the DRN induced the long-latency and long-lasting inhibition of the neuronal firing of the IGL cells that are characterized by rhythmic, slow-bursting activity in light conditions. The electrical destruction of the DRN resulted in an increase in the firing rate of the recorded IGL cells, whilst at the same time not affecting the rhythmic, bursting pattern of the activity. In the second group of animals, local neurotoxic lesion of serotonergic fibres was performed by injection of the toxin 5,7-dihydroxytryptamine into the IGL. After 10 days of postoperative recovery, electrophysiological experiments were performed on the toxin-treated rats. In these animals, electrical stimulation as well as electrical lesion of the DRN did not induce any change in the firing of the slowly bursting cells in the 5,7-dihydroxytryptamine-injected IGL. The results obtained provide evidence that inhibition of the IGL slowly bursting cells, by innervation from the dorsal raphe, is mediated by the release of serotonin. Furthermore, the observed serotonergic inhibition of the light-dependent activity of slowly bursting cells can contribute to the neuronal mechanism gating the information that flows through this nucleus to the vestibular, visuomotor, circadian and sleep/arousal systems, with which the IGL is strongly interconnected.
Asunto(s)
Potenciales de Acción/fisiología , Cuerpos Geniculados/citología , Inhibición Neural/fisiología , Neuronas/fisiología , Serotonina/metabolismo , 5,7-Dihidroxitriptamina/farmacología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/efectos de la radiación , Animales , Estimulación Eléctrica/métodos , Cuerpos Geniculados/lesiones , Inmunohistoquímica/métodos , Masculino , Inhibición Neural/efectos de los fármacos , Inhibición Neural/efectos de la radiación , Vías Nerviosas/fisiología , Vías Nerviosas/efectos de la radiación , Neuronas/clasificación , Neuronas/efectos de los fármacos , Periodicidad , Núcleos del Rafe/fisiología , Núcleos del Rafe/efectos de la radiación , Ratas , Ratas Wistar , Serotoninérgicos/farmacologíaRESUMEN
The monoamine neurotransmitter serotonin is released from spinal terminals of nucleus raphe magnus (NRM) neurons and important in sensory and motor control, but its pattern of release has remained unclear. Serotonin was measured by the high-resolution method of fast cyclic voltammetry (2 Hz) with carbon-fiber microelectrodes in lumbar segments (L3-L6) of halothane-anesthetized rats during electrical stimulation of the NRM. Because sites of serotonin release are often histologically remote from membrane transporters and receptors, rapid emergence into aggregate extracellular space was expected. Increased monoamine oxidation currents were found in 94% of trials of 50-Hz, 20-s NRM stimulation across all laminae. The estimated peak serotonin concentration averaged 37.8 nM (maximum 287 nM), and was greater in dorsal and ventral laminae (I-III and VIII-IX) than in intermediate laminae (IV-VI). When measured near NRM-evoked changes, basal monoamine levels (relative to dorsal white matter) were highest in intermediate laminae, while changes in norepinephrine level produced by locus ceruleus (LC) stimulation were lowest in laminae II/III and VII. The NRM-evoked monoamine peak was linearly proportional to stimulus frequency (10-100 Hz). The peak often occurred before the stimulus ended (mean 15.6 s at 50 Hz, range 4-35 s) regardless of frequency, suggesting that release per impulse was constant during the rise but fell later. The latency from stimulus onset to electrochemical signal detection (mean 4.2 s, range 1-23 s) was inversely correlated with peak amplitude and directly correlated with time-to-peak. Quantitative modeling suggested that shorter latencies mostly reflected the time below detection threshold (5-10 nM), so that extrasynaptic serotonin was significantly elevated well within 1 s. Longer latencies (>5 s), which were confined to intermediate laminae, appeared mainly to be due to diffusion from distant sources. In conclusion, except possibly in intermediate laminae, serotonergic volume transmission is a significant mode of spinal control by the NRM.
Asunto(s)
Vías Aferentes/fisiología , Estimulación Eléctrica , Núcleos del Rafe/efectos de la radiación , Serotonina/metabolismo , Médula Espinal/metabolismo , Animales , Mapeo Encefálico , Relación Dosis-Respuesta en la Radiación , Potenciales Evocados/efectos de la radiación , Laminectomía/métodos , Región Lumbosacra , Masculino , Ratas , Tiempo de Reacción/efectos de los fármacos , Tiempo de Reacción/fisiología , Médula Espinal/efectos de la radiaciónRESUMEN
Retinal afferents to the dorsal raphe nucleus (DRN) have been described in a number of species, including Mongolian gerbils, but functional correlates of this optic pathway are unknown at present. To determine whether temporally modulated photostimulation can affect c-Fos expression in the gerbil DRN, quantitative analysis of c-Fos-immunoreactive (c-Fos-ir) neurons was conducted following 60-min exposure to pulsed (2 Hz) photostimulation at selected times over the 12:12 h light/dark cycle. For comparison, c-Fos expression was also analyzed in the subnuclei of the lateral geniculate complex and in the suprachiasmatic nucleus (SCN). In the DRN, a substantial reduction was observed in the number of c-Fos immunoreactive (c-Fos-ir) neurons during the light period and early dark period in photostimulated vs. control animals. Similar results were obtained in the intergeniculate leaflet (IGL) and ventral lateral geniculate (VLG). However, no significant changes were observed in the number of c-Fos-ir neurons in the dorsal lateral geniculate nucleus or suprachiasmatic nucleus (SCN) following photostimulation, except for an increase in the middle of the dark period. These findings indicate that photic stimulation can lead to a suppression or down-regulation of c-Fos expression in the DRN that is probably mediated via the direct retinal pathway to the DRN in this species. The similarity between c-Fos expression profiles in the DRN and IGL/VGL suggest that efferent projections from the DRN may modulate c-Fos expression to visual stimulation in these subnuclei of the lateral geniculate complex.
Asunto(s)
Fototransducción/fisiología , Neuronas/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Núcleos del Rafe/metabolismo , Vías Visuales/metabolismo , Animales , Ritmo Circadiano/fisiología , Ritmo Circadiano/efectos de la radiación , Regulación hacia Abajo , Cuerpos Geniculados/citología , Cuerpos Geniculados/metabolismo , Cuerpos Geniculados/efectos de la radiación , Gerbillinae , Proteínas Inmediatas-Precoces/metabolismo , Proteínas Inmediatas-Precoces/efectos de la radiación , Inmunohistoquímica , Luz , Masculino , Neuronas/efectos de la radiación , Estimulación Luminosa , Proteínas Proto-Oncogénicas c-fos/efectos de la radiación , Núcleos del Rafe/citología , Núcleos del Rafe/efectos de la radiación , Núcleo Supraquiasmático/citología , Núcleo Supraquiasmático/metabolismo , Núcleo Supraquiasmático/efectos de la radiación , Vías Visuales/citología , Vías Visuales/efectos de la radiaciónRESUMEN
Orphanin FQ (OFQ) is an endogenous ligand for opioid receptor-like-1 (ORL1) receptor. Previous studies have shown that both OFQ immunoreactivity and preproorphanin FQ (ppOFQ) mRNA expression could be observed in the brain regions involved in pain modulation, e.g., nucleus of raphe magnus (NRM), dorsal raphe nucleus (DRN), and ventrolateral periaqueductal gray (vlPAG). It was reported that electroacupuncture (EA) has analgesic effect on neuropathic pain, and the analgesic effect was mediated by the endogenous opioid peptides. In the present study, we investigated the effects of EA on the changes of OFQ in the neuropathic pain rats. In the sciatic nerve chronic constriction injury (CCI) model, we investigated the changes of ppOFQ mRNA and OFQ immunoreactivity in NRM after EA by in situ hybridization (ISH) and immunohistochemistry methods, respectively. Then, the ppOFQ mRNA-positive and OFQ immunoreactive cells were counted under a computerized image analysis system. The results showed that expression of ppOFQ mRNA decreased and OFQ immunoreactivity increased after EA treatment in the neuropathic pain rats. These results indicated that EA modulated OFQ synthesis and OFQ peptide level in NRM of the neuropathic pain rats.
Asunto(s)
Electroacupuntura , Péptidos Opioides/metabolismo , Manejo del Dolor , Dolor/metabolismo , Núcleos del Rafe/efectos de la radiación , Análisis de Varianza , Animales , Inmunohistoquímica/métodos , Hibridación in Situ/métodos , Masculino , Péptidos Opioides/genética , Dolor/etiología , ARN Mensajero/metabolismo , Núcleos del Rafe/metabolismo , Ratas , Ratas Sprague-Dawley , Neuropatía Ciática/complicaciones , Neuropatía Ciática/terapia , NociceptinaRESUMEN
Animal studies examining the effects of stress upon brain serotonergic neurons have not presented a clearcut and consistent picture. One stressor that has been shown to exert a consistently strong effect on serotonin release and c-fos activation in the dorsal raphe nucleus of rats is a series of inescapable electrical shocks. Using immunohistochemical double labeling for c-fos activation and serotonin, we examined the effects of delivering 100 inescapable tailshocks to rats on serotonergic neuronal activation throughout the brainstem raphe system. This stimulus exerted a consistent and strong activation of the entire midline brain stem system of serotonergic neurons. The implications of these findings for animal models of human psychopathology are discussed.
Asunto(s)
Electrochoque/métodos , Neuronas/efectos de la radiación , Núcleos del Rafe/efectos de la radiación , Serotonina/metabolismo , Animales , Recuento de Células , Inmunohistoquímica/métodos , Masculino , Neuronas/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Núcleos del Rafe/citología , Ratas , Ratas Sprague-DawleyRESUMEN
Recent findings have revealed very slow (<0.5 Hz) oscillatory phenomena in the structures of the brain visual system. It has been proposed that very slow brain potentials in an extremely slow domain, less than 0.1 Hz, recorded from the lateral geniculate complex and primary visual cortex are associated with periodic influences originating from the locus coeruleus and dorsal raphe nucleus. The present study was performed to test the hypothesis that extremely slow brain potential oscillatory patterns in the locus coeruleus and dorsal raphe nucleus during several types of visual stimulation--light exposure, darkness, and photostimulation--are similar to those in the primary visual cortex and lateral geniculate complex under the same conditions of illumination. The results support this hypothesis. Specifically, spectral patterns of multisecond oscillations in the range of 0.02-0.04 Hz and fluctuations in the domain of minutes (below 0.002 Hz) were present in both the locus coeruleus and dorsal raphe nucleus and were similar to those found in the primary visual cortex and lateral geniculate complex. Additionally, we detected significant increases in the power spectra of multisecond oscillations in both nuclei in response to photostimulation (P<0.05). Our tentative conclusion is that extremely slow potentials in the locus coeruleus and dorsal raphe nucleus contribute to the regulation of extremely slow activity in the brain visual system.
Asunto(s)
Potenciales de Acción/efectos de la radiación , Iluminación/métodos , Locus Coeruleus/efectos de la radiación , Núcleos del Rafe/efectos de la radiación , Potenciales de Acción/fisiología , Animales , Locus Coeruleus/fisiología , Masculino , Estimulación Luminosa , Núcleos del Rafe/fisiología , RatasRESUMEN
Earlier work from this laboratory had shown that LSD caused significant increases in rat brain serotonin (5-HT). The increase was later localized to a subsynaptosomal fraction consisting largely of synaptic vesicles. However, the source of the increase and the mechanism by which LSD caused the enhanced 5-HT binding or retention had not been elucidated. The present study was undertaken to evaluate the serotonergic effects of LSD following destruction of raphe nuclei with radiofrequency lesions. When LSD was given to animals with large midbrain raphe lesions, it caused significant increases in forebrain of cortical 5-HT up to 48 hr, or 7 days post-lesion, respectively. It was concluded that an intact cell body is not necessary for the expression of the LSD-mediated increases in 5-HT occurring in the nerve-ending. The possible mechanisms by which LSD could act directly at the nerve-ending are discussed.