RESUMEN
Stereotaxic injection has been widely used for direct delivery of compounds or viruses to targeted brain areas in rodents. Direct targeting of serotonergic neurons in the dorsal raphe nucleus (DRN) can cause excessive bleeding and animal death, due to its location below the superior sagittal sinus (SSS). This protocol describes the generation of a DRN serotonergic neuron-lesioned mouse model (>90% survival rate) with stable loss of >70% 5-HT-positive cells in the DRN. The lesion is induced by stereotaxic injection of a selective serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) into the DRN using an angled approach (30° in the anterior/posterior direction) to avoid injury to the SSS. DRN serotonergic neuron-lesioned mice display anxiety-associated behavior alterations, which helps to confirm success of the DRN lesion surgery. This method is used here for DRN lesions, but it can also be used for other stereotaxic injections that require angular injections to avoid midline structures. This DRN serotonergic neuron-lesioned mouse model provides a valuable tool for understanding the role of serotonergic neurons in the pathogenesis of psychiatric disorders, such as generalized anxiety disorder and major depressive disorder.
Asunto(s)
5,7-Dihidroxitriptamina/administración & dosificación , Núcleo Dorsal del Rafe/efectos de los fármacos , Neuronas Serotoninérgicas/fisiología , Técnicas Estereotáxicas , 5,7-Dihidroxitriptamina/farmacología , Animales , Conducta Animal/efectos de los fármacos , Modelos Animales de Enfermedad , Masculino , Ratones Endogámicos C57BLRESUMEN
Hyperacusis may be defined as diminishing tolerance to moderate and high intensity sounds in people with normal hearing sensitivity. Serotonin plays a critical role in some of auditory tasks including startle reflex and prepulse inhibition. Serotonin deficiency can cause some diseases which can coincide with hyperacusis. The aim of the present study was to investigate the probable influence of serotonergic depletion in nucleus accumbens (NAcc) on the startle reflex. The startle reflexes were examined in Wistar rats (n: 48) in different intensities with and without the background noise. The amplitude of startle reflex significantly increased in NAcc-injected rats without background noise, while this difference disappeared in the presence of background noise in all intensities. These data proposed that the injection of 5, 7-Dihydroxytryptamine (5, 7-DHT) into nucleus accumbens will cause hyperacusis-like behavior, and strengthens the possibility of the role of serotonin and nucleus accumbens in hyperacusis.
Asunto(s)
5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/efectos adversos , Hiperacusia/inducido químicamente , Núcleo Accumbens/efectos de los fármacos , Estimulación Acústica , Animales , Inyecciones Intraventriculares , Masculino , Ratas , Reflejo de Sobresalto/efectos de los fármacosRESUMEN
BACKGROUND: For centuries, cannabinoids have been known to be effective in pain states. Itch and pain are two sensations sharing a lot in common. OBJECTIVE: The goal of this research was to observe whether the cannabinoid agonist WIN 55,212-2 reduces serotonin-induced scratching behaviour and whether neurotoxic destruction of descending serotonergic and noradrenergic pathways mediate the antipruritic effect of WIN 55,212-2. Material and methods Scratching behaviour was induced by intradermal injection of serotonin (50 µg/50 µl/mouse) to Balb/c mice. The neurotoxins 5,7-dihydroxytryptamine (5,7-DHT, 50 µg/mouse) and 6-hydroxydopamine (6-OHDA, 20 µg/mouse) are applied intrathecally to deplete serotonin and noradrenaline in the spinal cord. WIN 55,212-2 (1, 3, 10 mg/kg, i.p.) dose-dependently attenuated serotonin-induced scratches. Neurotoxic destruction of neither the serotonergic nor the noradrenergic systems by 5,7-DHT and 6-OHDA, respectively, had any effect on the antipruritic action of WIN 55,212-2. CONCLUSION: Our findings indicate that cannabinoids dose-dependently reduce serotonin-induced scratching behaviour and neurotoxic destruction of descending inhibitory pathways does not mediate this antipruritic effect.
Asunto(s)
Antipruriginosos/administración & dosificación , Benzoxazinas/administración & dosificación , Agonistas de Receptores de Cannabinoides/administración & dosificación , Morfolinas/administración & dosificación , Naftalenos/administración & dosificación , Norepinefrina/fisiología , Prurito/fisiopatología , Serotonina/fisiología , 5,7-Dihidroxitriptamina/administración & dosificación , Animales , Relación Dosis-Respuesta a Droga , Ratones , Ratones Endogámicos BALB C , Vías Nerviosas/efectos de los fármacos , Vías Nerviosas/fisiopatología , Oxidopamina/administración & dosificación , Prurito/inducido químicamente , Serotonina/administración & dosificación , Médula Espinal/efectos de los fármacos , Médula Espinal/fisiopatologíaRESUMEN
AIMS: Rheumatoid arthritis brings great burdens to the patients. In addition to the highly expensive treatment, they are commonly associated with severe side effects. In such context, the research for safe and affordable treatments is needed. MAIN METHODS: Arthritis was induced by CFA (0.5mg/mL) in female wistar rats. Trypsin was given p.o. (2.95mg/kg; 2mL) 24h after the intra-articular CFA injection. Articular incapacitation was measured daily by counting the paw elevation time (PET; s) during 1-min periods of stimulated walk, throughout the 7-days after intra-articular CFA injection. Articular diameter (AD) was accessed just after each PET measurement, taken the difference between naïve and diseased knee-joint diameter (cm). KEY FINDINGS: The present study showed that orally administered trypsin was able to reduce nociception and edema, effects that could be observed throughout the evaluation period. These effect, however, were not observed in animals underwent subdiaphragmatic vagotomy, suggesting a vagal mediation for trypsin effects. Likewise, these effects were blocked in rats which received intrathecal injection of the neurotoxins 5,7-dihydroxytryptamine or 6-hydroxydopamine, suggesting the involvement of spinal amines from axon terminals. SIGNIFICANCE: The present study proposes that oral trypsin may cause vagal activation, followed by the activation of descending inhibitory pathways and such mechanism may lead to a novel approach for the treatment of arthritis.
Asunto(s)
Analgésicos/uso terapéutico , Artritis Experimental/tratamiento farmacológico , Artritis Reumatoide/tratamiento farmacológico , Edema/tratamiento farmacológico , Nocicepción/efectos de los fármacos , Tripsina/uso terapéutico , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacología , Administración Oral , Adrenérgicos/administración & dosificación , Adrenérgicos/farmacología , Analgésicos/administración & dosificación , Analgésicos/farmacología , Animales , Artritis Experimental/complicaciones , Artritis Reumatoide/complicaciones , Edema/complicaciones , Femenino , Inyecciones Espinales , Oxidopamina/administración & dosificación , Oxidopamina/farmacología , Ratas Wistar , Serotoninérgicos/administración & dosificación , Serotoninérgicos/farmacología , Tripsina/administración & dosificación , Tripsina/farmacología , VagotomíaRESUMEN
Hyperactivation of the amygdala is implicated in anxiety and mood disorders, but the precise underlying mechanisms are unclear. We previously reported that depletion of serotonin (5-hydroxytryptamine, 5-HT) in the basolateral nucleus of the amygdala (BLA) using the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) potentiated learned fear and increased glutamate receptor (Glu) expression in BLA. Here we investigated the hypothesis that CaMKII facilitates anxiety-like behavior and increased Glu/AMPA receptor subunit A1 (GluA1) expression following depletion of 5-HT in the BLA. Infusion of 5,7-DHT into the BLA resulted in anxiety-like behavior in the open field test (OFT) and increased the phosphorylation of CaMKIIα (Thr-286) in the BLA. Knockdown of the CaMKIIα subunit using adeno-associated virus (AAV)-delivered shRNAi concomitantly attenuated anxiety-like behavior in the OFT and decreased GluA1 expression in the BLA. Our results suggest that the CaMKII signaling plays a key role in low 5-HT-induced anxiety and mood disturbances, potentially through regulation of GluA1 expression in the BLA.
Asunto(s)
Ansiedad/metabolismo , Complejo Nuclear Basolateral/metabolismo , Quinasa de la Proteína Quinasa Dependiente de Calcio-Calmodulina/metabolismo , Receptores AMPA/metabolismo , Serotonina/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , Animales , Ansiedad/inducido químicamente , Masculino , Fosforilación , Ratas , Ratas Sprague-Dawley , Receptores AMPA/genética , Serotoninérgicos/administración & dosificación , Regulación hacia ArribaRESUMEN
Withdrawal from amphetamine is associated with increased anxiety and sensitivity to stressors which are thought to contribute to relapse. Rats undergoing amphetamine withdrawal fail to exhibit stress-induced increases in serotonin (5-HT) release in the ventral hippocampus and show heightened anxiety-like behaviors. Therefore, we tested the hypothesis that reducing 5-HT levels in the ventral hippocampus is a causal mechanism in increasing anxiety-like behaviors during amphetamine withdrawal. First, we tested whether reducing 5-HT levels in the ventral hippocampus directly increases anxiety behavior. Male rats were bilaterally infused with 5,7-dihydroxytryptamine (5,7-DHT) into the ventral hippocampus, which produced a 83% decrease in ventral hippocampus 5-HT content, and were tested on the elevated plus maze (EPM) for anxiety-like behavior. Reducing ventral hippocampus 5-HT levels decreased the time spent in the open arms of the maze, suggesting that diminished ventral hippocampus 5-HT levels increases anxiety-like behavior. Next, we tested whether increasing 5-HT levels in the ventral hippocampus reverses anxiety behavior exhibited by rats undergoing amphetamine withdrawal. Rats were treated daily with either amphetamine (2.5-mg/kg, i.p.) or saline for 2weeks, and at 2weeks withdrawal, were infused with the selective serotonin reuptake inhibitor paroxetine (0.5µM) bilaterally into the ventral hippocampus and tested for anxiety-like behavior on the EPM. Rats pre-treated with amphetamine exhibited increased anxiety-like behavior on the EPM. This effect was reversed by ventral hippocampus infusion of paroxetine. Our results suggest that 5-HT levels in the ventral hippocampus are critical for regulating anxiety behavior. Increasing 5-HT levels during withdrawal may be an effective strategy for reducing anxiety-induced drug relapse.
Asunto(s)
Trastornos Relacionados con Anfetaminas/metabolismo , Ansiedad/metabolismo , Hipocampo/metabolismo , Serotoninérgicos/farmacología , Serotonina/metabolismo , Síndrome de Abstinencia a Sustancias/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacología , Anfetamina/administración & dosificación , Anfetamina/farmacología , Animales , Ansiedad/prevención & control , Estimulantes del Sistema Nervioso Central/administración & dosificación , Estimulantes del Sistema Nervioso Central/farmacología , Modelos Animales de Enfermedad , Hipocampo/efectos de los fármacos , Masculino , Paroxetina/administración & dosificación , Paroxetina/farmacología , Ratas , Ratas Sprague-Dawley , Serotoninérgicos/administración & dosificaciónRESUMEN
Coping is defined as the behavioral and physiological effort made to master stressful situations. The ability to cope with stress leads either to healthy or to pathogenic outcomes. The medial prefrontal cortex (mpFC) and amygdala are acknowledged as having a major role in stress-related behaviors, and mpFC has a critical role in the regulation of amygdala-mediated arousal in response to emotionally salient stimuli. Prefrontal cortical serotonin (5-hydroxytryptamine (5-HT)) is involved in corticolimbic circuitry, and GABA has a major role in amygdala functioning. Here, using mice, it was assessed whether amygdalar GABA regulation by prefrontal 5-HT is involved in processing stressful experiences and in determining coping outcomes. First (experiment 1), bilateral selective 5-HT depletion in mpFC of mice reduced GABA release induced by stress in basolateral amygdala (BLA) and passive coping in the Forced Swimming Test (FST) (experiment 2). Moreover, prefrontal-amygdala disconnection procedure that combined a selective unilateral 5-HT depletion of mpFC and infusion of an inhibitor of GABA synthesis into the contralateral BLA, thereby to disrupt prefrontal-amygdalar serial connectivity bilaterally, showed that disconnection selectively decreases immobility in the FST. These results point to prefrontal/amygdala connectivity mediated by 5-HT and GABA transmission as a critical neural mechanism in stress-induced behavior.
Asunto(s)
Adaptación Psicológica/fisiología , Amígdala del Cerebelo/fisiología , Corteza Prefrontal/fisiología , Serotonina/metabolismo , Estrés Psicológico/fisiopatología , Estrés Psicológico/psicología , Ácido gamma-Aminobutírico/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacología , Adaptación Psicológica/efectos de los fármacos , Alilglicina/administración & dosificación , Alilglicina/farmacología , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/metabolismo , Animales , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Dopamina/metabolismo , Antagonistas del GABA/farmacología , Pérdida de Tono Postural/efectos de los fármacos , Pérdida de Tono Postural/fisiología , Masculino , Ratones , Microinyecciones , Vías Nerviosas/efectos de los fármacos , Vías Nerviosas/metabolismo , Vías Nerviosas/fisiología , Norepinefrina/metabolismo , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Estrés Psicológico/metabolismoRESUMEN
Serotonin neurons of the caudal raphe facilitate ventilatory and sympathetic responses that develop following blood loss in conscious rats. Here, we tested whether serotonin projections to the caudal portion of the dorsomedial brain stem (including regions of the nucleus tractus solitarius that receive cardiovascular and chemosensory afferents) contribute to cardiorespiratory compensation following hemorrhage. Injections of the serotonin neurotoxin 5,7-dihydroxytryptamine produced >90% depletion of serotonin nerve terminals in the region of injection. Withdrawal of â¼21% of blood volume over 10 min produced a characteristic three-phase response that included 1) a normotensive compensatory phase, 2) rapid sympathetic withdrawal and hypotension, and 3) rapid blood pressure recovery accompanied by slower recovery of heart rate and sympathetic activity. A gradual tachypnea developed throughout hemorrhage, which quickly reversed with the advent of sympathetic withdrawal. Subsequently, breathing frequency and neural minute volume (determined by diaphragmatic electromyography) declined below baseline following termination of hemorrhage but gradually recovered over time. Lesioned rats showed attenuated sympathetic and ventilatory responses during early compensation and later recovery from hemorrhage. Both ventilatory and sympathetic responses to chemoreceptor activation with potassium cyanide injection were attenuated by the lesion. In contrast, the gain of sympathetic and heart rate baroreflex responses was greater, and low-frequency oscillations in blood pressure were reduced after lesion. Together, the data are consistent with the view that serotonin innervation of the caudal dorsomedial brain stem contributes to sympathetic compensation during hypovolemia, possibly through facilitation of peripheral chemoreflex responses.
Asunto(s)
Barorreflejo , Células Quimiorreceptoras/metabolismo , Hemorragia/metabolismo , Bulbo Raquídeo/metabolismo , Terminales Presinápticos/metabolismo , Ventilación Pulmonar , Neuronas Serotoninérgicas/metabolismo , Sistema Nervioso Simpático/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , Adaptación Fisiológica , Animales , Presión Sanguínea , Células Quimiorreceptoras/efectos de los fármacos , Modelos Animales de Enfermedad , Frecuencia Cardíaca , Hemorragia/patología , Hemorragia/fisiopatología , Hipotensión/metabolismo , Hipotensión/fisiopatología , Hipovolemia/metabolismo , Hipovolemia/fisiopatología , Inyecciones , Riñón/inervación , Masculino , Bulbo Raquídeo/efectos de los fármacos , Bulbo Raquídeo/patología , Bulbo Raquídeo/fisiopatología , Vías Nerviosas/metabolismo , Vías Nerviosas/fisiopatología , Cianuro de Potasio/administración & dosificación , Terminales Presinápticos/efectos de los fármacos , Terminales Presinápticos/patología , Ventilación Pulmonar/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Recuperación de la Función , Neuronas Serotoninérgicas/efectos de los fármacos , Neuronas Serotoninérgicas/patología , Serotoninérgicos/administración & dosificación , Sistema Nervioso Simpático/efectos de los fármacos , Sistema Nervioso Simpático/fisiopatología , Factores de TiempoRESUMEN
The prefrontal cortex and the nucleus accumbens are two brain sites which are known to be involved in the modulation of the acoustic startle response. In particular, the release of monoaminergic transmitters within these brain sites plays an important role in prepulse inhibition of the startle response which serves as an operational measure of sensorimotor gating. Like for dopamine, it is well established that serotonin transmission plays an important role in prepulse inhibition. However, there are only few studies investigating the effects of local manipulation of serotonin transmission on prepulse inhibition. The aim of the present study was to test whether prepulse inhibition or the startle response itself was affected by serotonergic depletion of either the prefrontal cortex or the nucleus accumbens. Serotonergic depletion was induced by local injections of 5,7-dihydroxytryptamine and verified by ex vivo analysis of transmitter levels by high pressure liquid chromatography. In our behavioural tests, we found that 5,7-dihydroxytryptamine into the prefrontal cortex decreased prepulse inhibition, whereas injections into the nucleus accumbens facilitated prepulse inhibition. The time course of these behavioural effects, as well as the transmitter level changes within the different brain sites was very different. Most interestingly, 5,7-dihydroxytryptamine injections into the nucleus accumbens affect serotonin and dopamine levels in both, nucleus accumbens and prefrontal cortex. Taken together, the present study supports an important role of serotonin in the modulation of prepulse inhibition and baseline startle magnitude. However, the observed changes cannot be attributed to a specific brain site since our data clearly show that local 5,7-dihydroxytryptamine injections also affect transmitter levels in brain sites away from the injection site.
Asunto(s)
5,7-Dihidroxitriptamina/administración & dosificación , Cognición/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Corteza Prefrontal/efectos de los fármacos , Reflejo de Sobresalto/efectos de los fármacos , Serotoninérgicos/administración & dosificación , Estimulación Acústica , Análisis de Varianza , Animales , Cateterismo , Cromatografía Líquida de Alta Presión , Cognición/fisiología , Dopamina/metabolismo , Ácido Hidroxiindolacético/metabolismo , Masculino , Núcleo Accumbens/metabolismo , Corteza Prefrontal/metabolismo , Ratas , Ratas Sprague-Dawley , Reflejo de Sobresalto/fisiología , Serotonina/metabolismoRESUMEN
Central serotonin (5-HT) function is thought to be a critical component of behavioral inhibition and impulse control. However, in recent clinical studies, 5-HT manipulations failed to affect stop-signal reaction time (SSRT), which is a fundamental process in behavioral inhibition. We investigated the effect of central 5-HT depletion (intracerebroventricular 5,7-dihydroxytryptamine) in rats on two aspects of behavioral inhibition, SSRT and 'waiting', using the stop-signal task. 5-HT depletion had no effects on SSRT or any other primary measure on the stop-signal task. However, within the same task, there was a deficit in 'waiting' in 5-HT-depleted rats when they were required to withhold from responding in the terminal element of the stop-signal task for an extended period. D-Amphetamine had dose-dependent, but not 5-HT-dependent effects on SSRT. Conversely, the dose that tended to improve, or decrease, SSRT (0.3 mg/kg) impaired the ability to wait, again independently of 5-HT manipulation. These findings suggest that SSRT and 'waiting' are distinct measures of behavioral inhibition, and show that 5-HT is critical for some forms of behavioral inhibition but not others. This has significant implications for the treatment of conditions such as attention deficit and hyperactivity disorder, substance abuse, and affective disorders, in which inhibitory and impulse-control deficits are common.
Asunto(s)
Encéfalo/fisiopatología , Conducta Impulsiva/fisiopatología , Actividad Motora , Tiempo de Reacción , Serotonina/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , Análisis de Varianza , Animales , Encéfalo/efectos de los fármacos , Condicionamiento Operante , Dextroanfetamina/administración & dosificación , Dopamina/metabolismo , Inhibidores de Captación de Dopamina/administración & dosificación , Relación Dosis-Respuesta a Droga , Inyecciones Intraventriculares , Masculino , Norepinefrina/metabolismo , Ratas , Serotoninérgicos/administración & dosificaciónRESUMEN
RATIONALE: Selective 5-ht(6) receptor antagonists like Ro 04-6790 prolong memory in many rodent preclinical paradigms, possibly by blocking tonic 5-HT-evoked GABA release and allowing disinhibition of cortico-limbic glutamatergic and cholinergic neurones. If this is the case, behavioural responses to Ro 04-6790 should be abolished by depletion of endogenous 5-HT, and selective lesions of dorsal raphé (DR) or median raphé (MR) 5-HT pathways would allow the neuroanatomical substrates underlying the cognitive effects of 5-ht(6) receptor antagonists to be elucidated. OBJECTIVES: This study compared the effect of Ro 04-6790 on novel object discrimination (NOD) before and after sham or 5,7-dihydroxytryptamine (5,7-DHT)-induced lesions produced by injection into the lateral ventricles (LV), DR or MR. MATERIALS AND METHODS: NOD tests used a 4 h inter-trial interval (ITI) and Ro 04-6790 (10 mg kg(-1) i.p.) was administered 20 min before the familiarization trial. Brain region-specific 5-HT depletion was assessed by high performance liquid chromatography with electrochemical detection (HPLC-ED). RESULTS: Widespread LV or selective MR, but not DR lesions, abolished the ability of Ro 04-6790 to delay natural forgetting. Successful performance of all lesioned rats in subsequent 'drug-free' NOD tests using a 1 h ITI excluded the possibility of any confounding effects on visual acuity or motivation. CONCLUSIONS: The ability of Ro 04-6790 to prolong object recognition memory requires blockade of MR 5-HT function. Because DR lesions did not produce the expected depletion of striatal 5-HT an additional contribution of DR inputs to this region cannot be completely excluded.
Asunto(s)
Cognición/efectos de los fármacos , Discriminación en Psicología/efectos de los fármacos , Desempeño Psicomotor/efectos de los fármacos , Psicotrópicos/farmacología , Pirimidinas/farmacología , Receptores de Serotonina/efectos de los fármacos , Antagonistas de la Serotonina/farmacología , Serotonina/fisiología , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacología , Análisis de Varianza , Animales , Peso Corporal/efectos de los fármacos , Química Encefálica/efectos de los fármacos , Aprendizaje Discriminativo/efectos de los fármacos , Inyecciones Intraventriculares , Masculino , Núcleos del Rafe/fisiología , Ratas , Serotoninérgicos/administración & dosificación , Serotoninérgicos/farmacologíaRESUMEN
BACKGROUND: Regulation of pain states is, in part, dependent upon plastic changes in neurones within the superficial dorsal horn. There is also compelling evidence that pain states are under the control of descending projections from the brainstem. While a number of transcription factors including Methyl-CpG-binding protein 2 (MeCP2), Zif268 and Fos have been implicated in the regulation of dorsal horn neurone sensitization following injury, modulation of their activity by descending controls has not been investigated. RESULTS: Here, we describe how descending controls regulate MeCP2 phosphorylation (P-MeCP2), known to relieve transcriptional repression by MeCP2, and Zif268 and Fos expression in the rat superficial dorsal horn, after CFA injection into the hind paw. First, we report that CFA significantly increased P-MeCP2 in Lamina I and II, from 30 min post injection, with a maximum reached after 1 h. The increase in P-MeCP2 paralleled that of Zif268 and Fos, and P-MeCP2 was expressed in large sub-populations of Zif268 and Fos expressing neurones. Serotonergic depletion of the lumbar spinal cord with 5,7 di-hydroxytryptamine creatinine sulphate (5,7-DHT) reduced the inflammation evoked P-MeCP2 in the superficial dorsal horn by 57%, and that of Zif268 and Fos by 37.5% and 30% respectively. Although 5,7-DHT did not change primary thermal hyperalgesia, it significantly attenuated mechanical sensitivity seen in the first 24 h after CFA. CONCLUSION: We conclude that descending serotonergic pathways play a crucial role in regulating gene expression in the dorsal horn and mechanical sensitivity associated with an inflammatory pain state.
Asunto(s)
Mediadores de Inflamación/administración & dosificación , Proteína 2 de Unión a Metil-CpG/metabolismo , Células del Asta Posterior/metabolismo , Células del Asta Posterior/patología , Serotonina/fisiología , Médula Espinal/metabolismo , Médula Espinal/patología , 5,7-Dihidroxitriptamina/administración & dosificación , Adyuvantes Inmunológicos/administración & dosificación , Animales , Adyuvante de Freund/administración & dosificación , Masculino , Proteína 2 de Unión a Metil-CpG/biosíntesis , Proteína 2 de Unión a Metil-CpG/genética , Fosforilación , Ratas , Ratas Sprague-Dawley , Serotonina/efectos adversosRESUMEN
In this study we have explored differences in animal reactivity to conditioned aversive stimuli using the conditioned fear test (a contextual fear-freezing response), in rats subjected to the selective lesion of the prefrontal cortex serotonergic innervation, and differing in their response to the acute painful stimulation, a footshock (HS--high sensitivity rats, and LS--low sensitivity rats, selected arbitrarily according to their behavior in the 'flinch-jump' pre-test). Local administration of serotonergic neurotoxin (5,7-dihydroxytryptamine) to the dorsomedial part of the prefrontal cortex caused a very strong, structure and neurotransmitter selective depletion of serotonin concentration. In HS rats, the serotonergic lesion significantly disinhibited rat behavior controlled by fear, enhanced c-Fos expression in the dorsomedial prefrontal area, and increased the concentration of GABA in the basolateral amygdala, measured in vivo after the testing session of the conditioned fear test. The LS animals revealed an opposite pattern of behavioral and biochemical changes after serotonergic lesion: an increase in the duration of a freezing response, and expression of c-Fos in the basolateral and central nuclei of amygdala, and a lower GABA concentration in the basolateral amygdala. In control conditions, c-Fos expression did not differ in LS and HS, naïve, not conditioned and not exposed to the test cage animals. The present study adds more arguments for the controlling role of serotonergic innervation of the dorsomedial part of the prefrontal cortex in processing emotional input by other brain centers. Moreover, it provides experimental data, which may help to better explain the anatomical and biochemical basis of differences in individual reactivity to stressful stimulation, and, possibly, to anxiolytic drugs with serotonergic or GABAergic profiles of action.
Asunto(s)
Conducta Animal/fisiología , Condicionamiento Clásico/fisiología , Reacción Cataléptica de Congelación/fisiología , Corteza Prefrontal/metabolismo , Serotonina/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/toxicidad , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/metabolismo , Amígdala del Cerebelo/fisiopatología , Animales , Conducta Animal/efectos de los fármacos , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Encéfalo/fisiopatología , Cromatografía Líquida de Alta Presión , Condicionamiento Clásico/efectos de los fármacos , Electrochoque/efectos adversos , Miedo/efectos de los fármacos , Miedo/fisiología , Reacción Cataléptica de Congelación/efectos de los fármacos , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Hipocampo/fisiopatología , Inmunohistoquímica , Masculino , Microdiálisis , Microinyecciones , Degeneración Nerviosa/inducido químicamente , Degeneración Nerviosa/fisiopatología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Umbral del Dolor , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/fisiopatología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ratas , Ratas Wistar , Serotoninérgicos/administración & dosificación , Serotoninérgicos/toxicidad , Ácido gamma-Aminobutírico/análisis , Ácido gamma-Aminobutírico/metabolismoRESUMEN
Intracerebroventricular injection of 5,7-dihydroxytryptamine (5,7-DHT) (150 microg; 4.5 microl/ventricle), a serotonergic neurotoxin, significantly decreased spontaneous alternation in Y-maze task and working memory in radial 8 arm-maze task, suggesting effects on short-term memory, without affecting long-term memory, explored by reference memory in radial 8 arm-maze task and step-through latency in multi-trial passive avoidance task. Parachlorophenylalanine (PCPA) (3 days treatment 200 microg, i.c.v.), a serotonin synthesis inhibitor, did not impair step-through-latency in multi-trial passive avoidance task, suggesting no effects on long-term memory. These results suggest that serotonin, among other neurotransmitters, play an important role in cognitive functions, especially short-term memory.
Asunto(s)
Encéfalo/metabolismo , Aprendizaje por Laberinto/fisiología , Memoria a Corto Plazo/fisiología , Retención en Psicología/fisiología , Serotonina/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , Animales , Reacción de Prevención/efectos de los fármacos , Reacción de Prevención/fisiología , Encéfalo/efectos de los fármacos , Fenclonina/farmacología , Inyecciones Intraventriculares , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Memoria a Corto Plazo/efectos de los fármacos , Ratas , Ratas Wistar , Retención en Psicología/efectos de los fármacos , Serotoninérgicos/administración & dosificaciónRESUMEN
It is well known that the dorsal raphe nucleus (DRN) sends serotonergic and nonserotonergic projections to target regions in the brain stem and forebrain, including the vestibular nuclei. Although retrograde tracing studies have reported consistently that there are differences in the relative innervation of different target regions by serotonergic and nonserotonergic DRN neurons, the relative termination patterns of these two projections have not been compared using anterograde tracing methods. The object of the present investigation was to trace anterogradely the individual serotonergic and nonserotonergic components of the projection from DRN to the vestibular nuclei in rats. To trace nonserotonergic DRN projections, animals were pretreated with the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT), and then, after 7 days, the anterograde tracer biotinylated dextran amine (BDA) was iontophoretically injected into the DRN. In animals treated with 5,7-DHT, nonserotonergic BDA-labeled fibers were found to descend exclusively within the ventricular plexus and to terminate predominantly within the periventricular aspect of the vestibular nuclei. Serotonergic DRN projections were traced by injecting 5,7-DHT directly into DRN, and amino-cupric-silver staining was used to visualize the resulting pattern of terminal degeneration. Eighteen hours after microinjection of 5,7-DHT into the DRN, fine-caliber degenerating serotonergic terminals were found within the region of the medial vestibular nucleus (MVN) that borders the fourth ventricle, and a mixture of fine- and heavier-caliber degenerating serotonergic terminals was located further laterally within the vestibular nuclear complex. These findings indicate that fine-caliber projections from serotonergic and nonserotonergic DRN neurons primarily innervate the periventricular regions of MVN, whereas heavier-caliber projections from serotonergic DRN neurons innervate terminal fields located in more lateral regions of the vestibular nuclei. Thus, serotonergic and nonserotonergic DRN axons target distinct but partially overlapping terminal fields within the vestibular nuclear complex, raising the possibility that these two DRN projection systems are organized in a manner that permits regionally-specialized regulation of processing within the vestibular nuclei.
Asunto(s)
Mapeo Encefálico , Vías Nerviosas/metabolismo , Núcleos del Rafe/metabolismo , Serotonina/metabolismo , Núcleos Vestibulares/metabolismo , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacocinética , Anatomía Regional , Animales , Transporte Biológico Activo/fisiología , Biotina/administración & dosificación , Biotina/análogos & derivados , Biotina/farmacocinética , Dextranos/administración & dosificación , Dextranos/farmacocinética , Colorantes Fluorescentes/administración & dosificación , Colorantes Fluorescentes/farmacocinética , Masculino , Vías Nerviosas/anatomía & histología , Núcleos del Rafe/anatomía & histología , Ratas , Ratas Long-Evans , Núcleos Vestibulares/anatomía & histologíaRESUMEN
PURPOSE: Although sound-induced (audiogenic) seizures in the genetically epilepsy-prone rat (GEPR) initially occur independent of the forebrain, repeated audiogenic seizures recruit forebrain seizure circuits in a process referred to as audiogenic kindling. In GEPR-3s, audiogenic kindling results in facial and forelimb (F&F) clonic seizures that are typical of forebrain seizures. However, in GEPR-9s, audiogenic kindling produces posttonic all-limb clonus not usually observed during forebrain seizures. We hypothesized that the more severe brainstem seizures of the GEPR-9 prevent the expression of F&F clonic seizures during audiogenic kindling. Therefore attenuation of audiogenic seizures during audiogenic kindling in GEPR-9s should allow F&F clonic seizures to be expressed. Likewise, intensifying audiogenic seizure severity in GEPR-3s should inhibit audiogenically kindled F&F clonic seizures. We have tested this hypothesis in the present study. METHODS: Lesions of the superior colliculus or treatment with low-dose phenytoin were used to suppress audiogenic seizure severity in GEPR-9s. Depletion of brain serotonin was used to increase the seizure severity in GEPR-3s. All GEPRs were then subjected to audiogenic kindling. Behavioral and electrographic seizures were assessed. RESULTS: Suppression of audiogenic seizure severity during audiogenic kindling in GEPR-9s increased the incidence forebrain seizure behavior. Kindled GEPR-9s that continued to display full tonic seizures did not exhibit forebrain convulsions, but did show posttonic clonus and forebrain seizure activity in the EEG. GEPR-3s chronically depleted of brain serotonin, along with displaying tonic brainstem seizures, tended to display less severe forebrain seizures during audiogenic kindling. CONCLUSIONS: These findings support the concept that severe brainstem seizures prevent the behavioral expression of forebrain seizures in audiogenically kindled GEPR-9s. It appears that the severe brainstem seizure of the GEPR-9 does not allow the forebrain seizure to manifest its typical behavioral concomitants despite electrographic evidence that spike-wave discharge is occurring in the forebrain.
Asunto(s)
Tronco Encefálico/fisiopatología , Epilepsia Refleja/genética , Epilepsia Refleja/fisiopatología , Excitación Neurológica/fisiología , Prosencéfalo/fisiopatología , Convulsiones/fisiopatología , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacología , Estimulación Acústica , Animales , Encéfalo/metabolismo , Química Encefálica/efectos de los fármacos , Tronco Encefálico/efectos de los fármacos , Modelos Animales de Enfermedad , Estimulación Eléctrica , Electrodos Implantados , Electroencefalografía/estadística & datos numéricos , Inyecciones Intraventriculares , Excitación Neurológica/efectos de los fármacos , Norepinefrina/metabolismo , Norepinefrina/fisiología , Fenitoína/farmacología , Prosencéfalo/efectos de los fármacos , Ratas , Convulsiones/diagnóstico , Serotonina/metabolismo , Serotonina/fisiología , Serotoninérgicos/administración & dosificación , Serotoninérgicos/farmacología , Índice de Severidad de la Enfermedad , Colículos Superiores/fisiopatologíaRESUMEN
Serotonergic dysregulation within the prefrontal cortex (PFC) is implicated in many neuropsychiatric disorders, but the precise role of serotonin within the PFC is poorly understood. Using a serial discrimination reversal paradigm, we showed that upon reversal, selective serotonin depletion of the marmoset PFC produced perseverative responding to the previously rewarded stimulus without any significant effects on either retention of a discrimination learned preoperatively or acquisition of a novel discrimination postoperatively. These results highlight the importance of prefrontal serotonin in behavioral flexibility and are highly relevant to obsessive-compulsive disorder, schizophrenia, and the cognitive sequelae of drug abuse in which perseveration is prominent.
Asunto(s)
Cognición , Aprendizaje Discriminativo , Corteza Prefrontal/fisiología , Serotonina/fisiología , 5,7-Dihidroxitriptamina/administración & dosificación , 5,7-Dihidroxitriptamina/farmacología , Animales , Conducta Animal , Encéfalo/metabolismo , Callithrix , Dopamina/metabolismo , Femenino , Lóbulo Frontal/metabolismo , Giro del Cíngulo/metabolismo , Ácido Hidroxiindolacético/metabolismo , Masculino , Corteza Motora/metabolismo , Norepinefrina/metabolismo , Oxidopamina/farmacología , Corteza Prefrontal/metabolismo , Desempeño Psicomotor , Recompensa , Serotonina/metabolismoRESUMEN
Although the selective toxicity of 5,7-dihydroxytryptamine (5,7-DHT) is thought to depend on the drug's transport into serotonin (5HT) neurons via the 5HT transporter, few studies have critically examined this postulation. We therefore evaluated if 5,7-DHT-induced reductions in 5HT concentrations and synthesis rate in rat brain are blocked by pretreatment with 5HT-selective reuptake inhibitors. Rats pretreated with desipramine (DMI) (to prevent norepinephrine depletion) received intracerebroventricular injections of 5,7-DHT (5, 50, 100, 200 microg/rat) 30 min after fluoxetine (20 mg/kg ip). Forty-eight hours later, they received m-hydroxybenzylhydrazine 30 min before sacrifice. The concentrations of 5HT and 5-hydroxytryptophan (5HTP, an index of 5HT synthesis) were measured in hypothalamus, cortex and brainstem. Each 5,7-DHT dose produced significant reductions in 5HT and 5HTP concentrations in all regions examined (5 microg reduced 5HT but not 5HTP), effects that were not blocked by fluoxetine. Two other 5HT reuptake blockers (chlorimipramine, alaproclate) also failed to block the 5HT and 5HTP depleting actions of 5,7-DHT. Desipramine blocked 5,7-DHT-induced norepinephrine (NE) depletion. Pretreatment with the 5HT receptor antagonist metergoline, or the 5HT(1A) agonist 8-hydroxy-(di-n-propylamino)tetralin (to slow 5HT neuronal firing rate) also failed to antagonize the 5HT depleting action of 5,7-DHT. Together, the data strongly suggest that the mechanism by which 5,7-DHT depletes the brain of serotonin does not involve 5HT-transporter-mediated concentration of neurotoxin in 5HT neurons, may not involve 5HT receptor interaction, and does not depend on the firing rate of the 5HT neuron.
Asunto(s)
5,7-Dihidroxitriptamina/farmacología , 8-Hidroxi-2-(di-n-propilamino)tetralin/análogos & derivados , Química Encefálica , Encéfalo/efectos de los fármacos , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Serotoninérgicos/farmacología , Serotonina/deficiencia , 5,7-Dihidroxitriptamina/administración & dosificación , 5-Hidroxitriptófano/metabolismo , 8-Hidroxi-2-(di-n-propilamino)tetralin/farmacología , Inhibidores de Captación Adrenérgica/farmacología , Animales , Encéfalo/anatomía & histología , Encéfalo/metabolismo , Cromatografía Líquida de Alta Presión/métodos , Desipramina/farmacología , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Interacciones Farmacológicas , Electroquímica/métodos , Inyecciones Intraventriculares/métodos , Masculino , Metergolina/farmacología , Ratas , Ratas Sprague-Dawley , Serotoninérgicos/administración & dosificación , Antagonistas de la Serotonina/farmacologíaRESUMEN
The involvement of spinopetal noradrenergic and serotonergic systems in antinociception induced by endomorphin-1 (EM-1) and endomorphin-2 (EM-2) given supraspinally or spinally were investigated in male CD-1 mice. Groups of mice were pretreated intrathecally (i.t.) with 6-hydroxydopamine (6-OHDA, 20 microg) or 5,7-dihydroxytryptamine (5,7-DHT, 50 microg) for 3 days before intracerebroventricular (i.c.v.) or i.t. injection of different doses of EM-1 or EM-2, and the tail-flick response was measured for antinociceptive effects. I.t. pretreatment with 6-OHDA for 3 days, which markedly depleted noradrenaline (NA) contents by more than 90%, but not serotonin (5-HT) in the spinal cord, completely abolished the antinociception induced by i.c.v.-administered EM-1 or EM-2. Intrathecal pretreatment with 5,7-DHT for 3 days, which markedly reduced 5-HT contents by more than 92%, but only reduced NA by 14 - 25% in the spinal cord, also markedly attenuated the antinociception induced by i.c.v.-administered EM-1 or EM-2. However, the antinociception induced by i.t.-administered EM-1 or EM-2 was not affected in either 6-OHDA or 5,7-DHT pretreated mice. It is concluded that NA and 5-HT in the spinal cord are involved in the antinociception induced by supraspinally, but not spinally administered EM-1 and EM-2.
Asunto(s)
5,7-Dihidroxitriptamina/administración & dosificación , Analgésicos/antagonistas & inhibidores , Oligopéptidos/antagonistas & inhibidores , Oxidopamina/administración & dosificación , Analgésicos/administración & dosificación , Animales , Relación Dosis-Respuesta a Droga , Inyecciones Intraventriculares , Inyecciones Espinales , Masculino , Ratones , Oligopéptidos/administración & dosificación , Dimensión del Dolor/efectos de los fármacos , Dimensión del Dolor/métodosRESUMEN
Using the microdialysis method, we investigated whether the levels of serotonin (5-hydroxytryptamine, 5-HT) and its metabolites, 5-hydroxyindoleacetic acid (5-HIAA) and 5-hydroxytryptophol (5-HTPL), in the locus coeruleus are influenced by tryptophan alone or simultaneous administration of tryptophan and ethanol. Tryptophan (50 mg/kg, i.p.) led to a significant increase in the levels of 5-HIAA, but not 5-HT in the locus coeruleus. However, ethanol (1.25 g/kg) had no effect on the levels of 5-HT and its metabolites. Combined administration of tryptophan and ethanol caused very marked increases in 5-HIAA and 5-HTPL levels in the locus coeruleus. A time lag in the increased 5-HIAA levels between tryptophan alone and tryptophan plus ethanol was observed. Moreover, 5-HIAA levels in the locus coeruleus induced by tryptophan were abolished by microinjection of 5,7-dihydroxytryptamine (150 microg/4 microl) into the dorsal raphe nucleus. Judging from the present results, the serotonergic afferents to the locus coeruleus may originate for about 20-30% from cell bodies located in the dorsal raphe nucleus. Teeth-chattering was significantly detected in the tryptophan plus ethanol-treated rats when compared with the tryptophan-treated rats, but not in the saline-treated controls. These results may suggest that the increased levels of 5-HIAA and 5-HTPL in the locus coeruleus induced by tryptophan are potentiated by ethanol, and that these levels are partly responsible for behavioral activation.