RESUMO
The dorsal raphe nucleus (DRN) receives dopaminergic inputs from the ventral tegmental area (VTA). Also, the DRN contains a small population of cells that express dopamine (DRNDA neurons). However, the physiological role of dopamine (DA) in the DRN and its interaction with serotonergic (5-HT) neurons is poorly understood. Several works have reported moderate levels of D1, D2, and D3 DA receptors in the DRN. Furthermore, it was found that the activation of D2 receptors increased the firing of putative 5-HT neurons. Other studies have reported that D1 and D2 dopamine receptors can interact with glutamate NMDA receptors, modulating the excitability of different cell types. In the present work, we used immunocytochemical techniques to determine the kind of DA receptors in the DRN. Additionally, we performed electrophysiological experiments in brainstem slices to study the effect of DA agonists on NMDA-elicited currents recorded from identified 5-HT DRN neurons. We found that D2 and D3 but not D1 receptors are present in this nucleus. Also, we demonstrated that the activation of D2-like receptors increases NMDA-elicited currents in 5-HT neurons through a mechanism involving phospholipase C (PLC) and protein kinase C (PKC) enzymes. Possible physiological implications related to the sleep-wake cycle are discussed.
Assuntos
Núcleo Dorsal da Rafe , Receptores de Dopamina D2 , Receptores de N-Metil-D-Aspartato , Neurônios Serotoninérgicos , Animais , Núcleo Dorsal da Rafe/metabolismo , Núcleo Dorsal da Rafe/efeitos dos fármacos , Receptores de Dopamina D2/metabolismo , Neurônios Serotoninérgicos/metabolismo , Neurônios Serotoninérgicos/efeitos dos fármacos , Neurônios Serotoninérgicos/fisiologia , Masculino , Receptores de N-Metil-D-Aspartato/metabolismo , Receptores de Dopamina D3/metabolismo , N-Metilaspartato/farmacologia , N-Metilaspartato/metabolismo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D1/agonistas , Agonistas de Dopamina/farmacologia , Ratos , Fosfolipases Tipo C/metabolismo , Ratos WistarRESUMO
Sleep disturbances and persistent pain conditions are public health challenges worldwide. Although it is well-known that sleep deficit increases pain sensitivity, the underlying mechanisms remain elusive. We have recently demonstrated the involvement of nucleus accumbens (NAc) and anterior cingulate cortex (ACC) in the pronociceptive effect of sleep restriction. In this study, we found that sleep restriction increases c-Fos expression in NAc and ACC, suggesting hyperactivation of these regions during prolonged wakefulness in male Wistar rats. Blocking adenosine A2A receptors in the NAc or GABAA receptors in the ventral tegmental area (VTA), dorsal raphe nucleus (DRN), or locus coeruleus (LC) effectively mitigated the pronociceptive effect of sleep restriction. In contrast, the blockade of GABAA receptors in each of these nuclei only transiently reduced carrageenan-induced hyperalgesia. Pharmacological activation of dopamine D2, serotonin 5-HT1A and noradrenaline alpha-2 receptors within the ACC also prevented the pronociceptive effect of sleep restriction. While pharmacological inhibition of these same monoaminergic receptors in the ACC restored the pronociceptive effect which had been prevented by the GABAergic disinhibition of the of the VTA, DRN or LC. Overall, these findings suggest that the pronociceptive effect of sleep restriction relies on increased adenosinergic activity on NAc, heightened GABAergic activity in VTA, DRN, and LC, and reduced inhibitory monoaminergic activity on ACC. These findings advance our understanding of the interplay between sleep and pain, shedding light on potential NAc-brainstem-ACC mechanisms that could mediate increased pain sensitivity under conditions of sleep impairment.
Assuntos
Núcleo Accumbens , Ratos Wistar , Privação do Sono , Área Tegmentar Ventral , Animais , Masculino , Privação do Sono/metabolismo , Privação do Sono/fisiopatologia , Ratos , Área Tegmentar Ventral/metabolismo , Área Tegmentar Ventral/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Núcleo Accumbens/efeitos dos fármacos , Receptor A2A de Adenosina/metabolismo , Hiperalgesia/metabolismo , Núcleo Dorsal da Rafe/metabolismo , Núcleo Dorsal da Rafe/efeitos dos fármacos , Giro do Cíngulo/metabolismo , Giro do Cíngulo/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-fos/metabolismo , Tronco Encefálico/metabolismo , Tronco Encefálico/efeitos dos fármacos , Locus Cerúleo/metabolismo , Locus Cerúleo/efeitos dos fármacos , Carragenina , Receptores de GABA-A/metabolismo , Receptores de Dopamina D2/metabolismo , Antagonistas do Receptor A2 de Adenosina/farmacologiaRESUMO
Disruption of the brain serotoninergic (5-HT) system during development induces long-lasting changes in molecular profile, cytoarchitecture, and function of neurons, impacting behavioral regulation throughout life. In male and female rats, we investigate the effect of neonatal tryptophan hydroxylase (TPH) inhibition by using para-chlorophenylalanine (pCPA) on the expression of 5-HTergic system components and neuropeptides related to adolescent social play behavior regulation. We observed sex-dependent 5-HT levels decrease after pCPA-treatment in the dorsal raphe nucleus (DRN) at 17 and 35 days. Neonatal pCPA-treatment increased playing, social and locomotory behaviors assessed in adolescent rats of both sexes. The pCPA-treated rats demonstrated decreased Crh (17 days) and increased Trh (35 days) expression in the hypothalamic paraventricular nucleus (PVN). There was sex dimorphism in Htr2c (17 days) and VGF (35 days) in the prefrontal cortex, with the females expressing higher levels of it than males. Our results indicate that neonatal pCPA-treatment results in a long-lasting and sex-dependent DRN 5-HT synthesis changes, decreased Crh, and increased Trh expression in the PVN, resulting in a hyperactivity-like phenotype during adolescence. The present work demonstrates that the impairment of TPH function leads to neurobehavioral disorders related to hyperactivity and impulsivity, such as attention deficit hyperactivity disorder (ADHD).
Assuntos
Núcleo Hipotalâmico Paraventricular , Serotonina , Ratos , Feminino , Masculino , Animais , Fenclonina/farmacologia , Núcleo Hipotalâmico Paraventricular/metabolismo , Serotonina/metabolismo , Núcleo Dorsal da Rafe/metabolismo , Triptofano Hidroxilase/metabolismoRESUMO
Morphine promotes neuroinflammation after NOD-like receptor protein 3 (NLRP3) oligomerization in glial cells, but the capacity of other opioids to induce neuroinflammation and its relationship to the development of analgesic tolerance is unknown. We studied the effects of morphine and fentanyl on NLRP3 inflammasome activation in glial and neuronal cells in the dorsal raphe nucleus (DRN), a region involved in pain regulation. Male Wistar rats received i.p. injections of morphine (10 mg/kg) or fentanyl (0.1 mg/kg) 3 × daily for 7 days and were tested for nociception. Two hours after the last (19th) administration, we analyzed NLRP3 oligomerization, caspase-1 activation and gasdermin D-N (GSDMD-N) expression in microglia (CD11b positive cells), astrocytes (GFAP-positive cells) and neurons (NeuN-positive cells). Tolerance developed to both opioids, but only fentanyl produced hyperalgesia. Morphine and fentanyl activated NLRP3 inflammasome in astrocytes and serotonergic (TPH-2-positive) neurons, but fentanyl effects were more pronounced. Both opioids increased GFAP and CD11b immunoreactivity, caspase-1 and GSDMD activation, indicating pyroptotic cell death. The opioid receptor antagonist (-)-naloxone, but not the TLR4 receptor antagonist (+)-naloxone, prevented microglia activation and NLRP3 oligomerization. Only (+)-naloxone prevented astrocytes' activation. The anti-inflammatory agent minocycline and the NLRP3 inhibitor MCC950 delayed tolerance to morphine and fentanyl antinociception and prevented fentanyl-induced hyperalgesia. MCC950 also prevented opioid-induced NLRP3 oligomerization. In conclusion, morphine and fentanyl differentially induce cell-specific activation of NLRP3 inflammasome and pyroptosis in the DRN through TLR4 receptors in astrocytes and through opioid receptors in neurons, indicating that neuroinflammation is involved in opioid-induced analgesia and fentanyl-induced hyperalgesia after repeated administrations.
Assuntos
Fentanila , Morfina , Analgésicos Opioides/farmacologia , Animais , Núcleo Dorsal da Rafe/metabolismo , Fentanila/farmacologia , Masculino , Morfina/farmacologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Proteínas NLR , Piroptose , Ratos , Ratos Wistar , Receptores Opioides/metabolismo , Receptor 4 Toll-Like/metabolismoRESUMO
Nociception alterations are frequent non-motor symptoms of the prodromal phase of Parkinson's disease (PD). The period for the onset of symptoms and the pathophysiological mechanisms underlying these alterations remain unclear. We investigated the course of nociception alterations in a progressive model of parkinsonism induced by reserpine (RES) in rats. Male Wistar rats (6-7 months) received 5 or 10 subcutaneous injections of RES (0.1 mg/kg) or vehicle daily for 20 days. Motor evaluation and nociceptive assessment were performed throughout the treatment. At the end of the treatment rats were euthanized, the brains removed and processed for immunohistochemical analysis (TH and c-Fos). The RES-treated rats exhibited an increased nociceptive response to mechanical and chemical stimulation in the electronic von Frey and formalin tests, respectively. Moreover, these alterations preceded the motor impairment observed in the catalepsy test. In addition, the RES treatment reduced the TH-immunoreactivity in the ventral tegmental area (VTA) and increased the c-Fos expression in the ventral-lateral periaqueductal gray (vlPAG), rostral ventral medulla (RVM) and dorsal raphe nucleus (DRN) after noxious stimuli induced by formalin. Taken together, our results reinforce that nociceptive changes are one of the early signs of PD and monoamine depletion in basal ganglia can be involved in the abnormal processing of nociceptive information in PD.
Assuntos
Núcleo Dorsal da Rafe/metabolismo , Atividade Motora/fisiologia , Nociceptividade/fisiologia , Doença de Parkinson Secundária/fisiopatologia , Substância Cinzenta Periaquedutal/metabolismo , Área Tegmentar Ventral/metabolismo , Animais , Modelos Animais de Doenças , Núcleo Dorsal da Rafe/fisiopatologia , Masculino , Doença de Parkinson Secundária/induzido quimicamente , Doença de Parkinson Secundária/metabolismo , Substância Cinzenta Periaquedutal/fisiopatologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Wistar , Reserpina , Tirosina 3-Mono-Oxigenase/metabolismo , Área Tegmentar Ventral/fisiopatologiaRESUMO
The serotoninergic system plays an important role in the ontogeny of the mammalian central nervous system, and changes in serotonin production during development may lead to permanent changes in brain cytoarchitecture and function. The present study investigated the programming effects of neonatal serotonin depletion on behavior and molecular components of the serotoninergic system in adult male and female rats. Subcutaneous para-chlorophenylalanine (pCPA) administration (100 mg kg-1) was performed daily on postnatal days 8-16 to deplete brain serotonin content. During adulthood, elevated plus-maze, open field, social interaction, forced swimming, and food, saline, and sucrose intake tests were performed. Relative expression of serotonin neurotransmission components in several brain areas was determined by qPCR. Additionally, serotonin immunofluorescence and neuropeptide mRNA expression were assessed in dorsal raphe (DRN) and paraventricular (PVN) nuclei, respectively. Rat performance in behavioral tests demonstrated a general increase in locomotor activity and active escape behavior as well as decreased anxiety-like behavior after neonatal brain serotonin depletion. The behavioral programming effects due to neonatal serotonin depletion were more pronounced in females than males. At the gene expression level, the mRNA of Tph1 and Tph2 were lower in DRN while Htr2c was higher in the amygdala of pCPA-treated males, while Htr1a, Htr2c, Oxt, Avp, Crh, and Trh were not different in any treatments or sex in PVN. The results indicate that neonatal serotonin depletion has long-term consequences on locomotion and anxiety-like behavior associated with long-lasting molecular changes in the brain serotoninergic system in adult rats.
Assuntos
Envelhecimento/patologia , Ansiolíticos/metabolismo , Serotonina/deficiência , Caracteres Sexuais , Tonsila do Cerebelo/metabolismo , Animais , Animais Recém-Nascidos , Peso Corporal , Encéfalo/metabolismo , Núcleo Dorsal da Rafe/metabolismo , Teste de Labirinto em Cruz Elevado , Comportamento Alimentar , Feminino , Regulação da Expressão Gênica , Masculino , Teste de Campo Aberto , Núcleo Hipotalâmico Paraventricular/metabolismo , Córtex Pré-Frontal/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Serotonina/metabolismo , Interação Social , NataçãoRESUMO
Previous studies showed that mecamylamine a noncompetitive and nonspecific blocker of nicotinic acetylcholine receptors (nAChRs), stimulates the activity of the dorsal raphe nucleus (DRN) serotonergic neurons and DRN serotonin (5-HT) release. In the present study, the mechanisms involved in these mecamylamine-induced effects were examined using electrophysiology and calcium-imaging studies, both performed in Wistar rat midbrain slices. Mecamylamine (0.5-9 µM), bath administered, increased the firing frequency of identified 5-HT DRN neurons by a maximum of 5% at 3 µM. This effect was accompanied by a 112 % increase in the frequency of spontaneous excitatory postsynaptic currents of 5-HT DRN neurons. It was blocked by the AMPA/kainate receptor blocker CNQX (10 µM) and by the specific α4ß2 nAChRs blocker dihydro-ß-erythroidine (100 nM) but was not affected by tetrodotoxin (TTX, 500 nM). Simultaneously, mecamylamine produced a 58 % decrease in the frequency of GABAergic spontaneous inhibitory postsynaptic currents, an effect that was not influenced by TTX. Calcium-imaging studies support the results obtained with the electrophysiological studies by showing that mecamylamine (3 µM) increases the activity of a cell population located in the midline of the DRN, which was sensitive to the inhibitory effects of 8-OH-DPAT, an agonist at 5-HT1A receptors. It is assumed that mecamylamine, in low concentrations, acts as an agonist of α4ß2 nAChRs present on the glutamatergic DRN terminals, thus increasing intra-raphe glutamate release. This stimulatory effect is reinforced by the decrease in DRN GABA release, which is dependent on the mecamylamine-induced blockade of α7 nAChRs located on DRN GABAergic terminals. We hypothesize that at least a part of mecamylamine antidepressant effects described in animal models of depression are mediated by an increase in DRN 5-HT release.
Assuntos
Potenciais de Ação/efeitos dos fármacos , Núcleo Dorsal da Rafe/efeitos dos fármacos , Bloqueadores Ganglionares/farmacologia , Mecamilamina/farmacologia , Neurônios Serotoninérgicos/efeitos dos fármacos , Animais , Cálcio/metabolismo , Núcleo Dorsal da Rafe/metabolismo , Masculino , Técnicas de Patch-Clamp , Ratos , Ratos Wistar , Neurônios Serotoninérgicos/metabolismoRESUMO
Pathophysiological mechanisms involved in orofacial pain and their relationship with emotional disorders have emerged as an important research area for multidisciplinary studies. In particular, temporomandibular disorders (TMD) have been evaluated clinically from both physiological and psychological perspectives. We hypothesized that an altered neuronal activity occurs in the amygdala and the dorsal raphe nucleus (DR), encephalic regions involved in the modulation of painful and emotional information. Adult male Wistar rats were used in an experimental complete Freund's adjuvant (CFA)-induced temporomandibular joint (TMJ) inflammation model. CFA was applied for 1 or 10 days, and the animals were euthanized for brain samples dissection for FosB/ΔFosB and parvalbumin (PV) immunostaining. Our results were consistent in showing that the amygdala and DR were activated in the persistent inflammatory phase (10 days) and that the expression of PV+ interneurons in the amygdala was decreased. In contrast, in the DR, the expression of PV+ interneurons was increased in persistent states of CFA-induced TMJ inflammation. Moreover, at 10 days of inflammation, there was an increased co-localization of PV+ and FosB/ΔFosB+ neurons in the basolateral and central nucleus of the amygdala. Different nuclei of the amygdala, as well as portions of the DR, were activated in the persistent phase (10 days) of TMJ inflammation. In conclusion, altered activity of the amygdala and DR was detected during persistent inflammatory nociception in the temporomandibular joint. These regions may be essential for both sensory and affective dimensions of orofacial pain.
Assuntos
Tonsila do Cerebelo/metabolismo , Núcleo Dorsal da Rafe/metabolismo , Parvalbuminas/metabolismo , Articulação Temporomandibular/fisiologia , Animais , Inflamação , Masculino , Neurônios , Ratos , Ratos Sprague-Dawley , Ratos WistarRESUMO
Pathophysiological mechanisms involved in orofacial pain and their relationship with emotional disorders have emerged as an important research area for multidisciplinary studies. In particular, temporomandibular disorders (TMD) have been evaluated clinically from both physiological and psychological perspectives. We hypothesized that an altered neuronal activity occurs in the amygdala and the dorsal raphe nucleus (DR), encephalic regions involved in the modulation of painful and emotional information. Adult male Wistar rats were used in an experimental complete Freund's adjuvant (CFA)-induced temporomandibular joint (TMJ) inflammation model. CFA was applied for 1 or 10 days, and the animals were euthanized for brain samples dissection for FosB/ΔFosB and parvalbumin (PV) immunostaining. Our results were consistent in showing that the amygdala and DR were activated in the persistent inflammatory phase (10 days) and that the expression of PV+ interneurons in the amygdala was decreased. In contrast, in the DR, the expression of PV+ interneurons was increased in persistent states of CFA-induced TMJ inflammation. Moreover, at 10 days of inflammation, there was an increased co-localization of PV+ and FosB/ΔFosB+ neurons in the basolateral and central nucleus of the amygdala. Different nuclei of the amygdala, as well as portions of the DR, were activated in the persistent phase (10 days) of TMJ inflammation. In conclusion, altered activity of the amygdala and DR was detected during persistent inflammatory nociception in the temporomandibular joint. These regions may be essential for both sensory and affective dimensions of orofacial pain.
Assuntos
Animais , Masculino , Ratos , Parvalbuminas/metabolismo , Articulação Temporomandibular/fisiologia , Núcleo Dorsal da Rafe/metabolismo , Tonsila do Cerebelo/metabolismo , Ratos Wistar , Ratos Sprague-Dawley , Inflamação , NeurôniosRESUMO
Animal studies have shown that antagonists of receptor 1 of Melanin-Concentrating Hormone (MCH-R1) elicit antidepressive-like behavior, suggesting that MCH-R1 might be a novel target for the treatment of depression and supports the hypothesis that MCHergic signaling regulates depressive-like behaviors. Consistent with the evidence that MCHergic neurons send projections to dorsal and median raphe nuclei, we have previously demonstrated that MCH microinjections in both nuclei induced a depressive-like behavior. Even though MCH neurons also project to Locus Coeruleus (LC), only a few studies have reported the behavioral and neurochemical effect of MCH into the LC. We studied the effects of MCH (100 and 200 ng) into the LC on coping-stress related behaviors associated with depression, using two different behavioral tests: the forced swimming test (FST) and the learned helplessness (LH). To characterize the functional interaction between MCH and the noradrenergic LC system, we also evaluated the neurochemical effects of MCH (100 ng) on the extracellular levels of noradrenaline (NA) in the medial prefrontal cortex (mPFC), an important LC terminal region involved in emotional processing. MCH administration into the LC elicited a depressive-like behavior evidenced in both paradigms. Interestingly, in the LH, MCH (100) elicited a significant increase in escape failures only in stressed animals. A significant decrease in prefrontal levels of NA was observed after MCH microinjection into the LC. Our results demonstrate that increased MCH signaling into the LC triggers depressive-like behaviors, especially in stressed animals. These data further corroborate the important role of MCH in the neurobiology of depression.