RESUMO
Hypocretin-1 and 2 (HCRT-1 and HCRT-2, respectively) are neuropeptides synthesized by neurons located in the postero-lateral hypothalamus, whose projections are widely distributed throughout the brain. The hypocretinergic (HCRTergic) system has been associated with the generation and maintenance of wakefulness, as well as with the promotion of motivated behaviors. In lactating rats, intra-cerebroventricular HCRT-1 administration stimulates maternal behavior, whilst lactation per se increases the expression of HCRT type 1 receptor (HCRT-R1). Due to the fact that HCRTergic receptors are expressed in the medial preoptic area (mPOA), a region critically involved in maternal behavior, we hypothesize that HCRT-1 promotes maternal behavior acting on this region. In order to evaluate this hypothesis, we assessed the maternal behavior of lactating rats following microinjections of HCRT-1 (10 or 100µM) and the selective HCRT-R1 antagonist SB-334867 (250µM) into the mPOA, during the first and second postpartum weeks. While intra-mPOA microinjections of HCRT-1 (100µM) increased corporal pup licking during the second postpartum week, the blockade of HCRT-R1 significantly decreased active components of maternal behavior, such as retrievals, corporal and ano-genital lickings, and increased the time spent in nursing postures in both postpartum periods. We conclude that HCRTergic system in the mPOA may stimulate maternal behavior, suggesting that endogenous HCRT-1 is necessary for the natural display of this behavior.
Assuntos
Lactação/metabolismo , Comportamento Materno/fisiologia , Receptores de Orexina/fisiologia , Orexinas/fisiologia , Área Pré-Óptica/metabolismo , Animais , Escala de Avaliação Comportamental , Benzoxazóis/farmacologia , Feminino , Região Hipotalâmica Lateral/citologia , Região Hipotalâmica Lateral/metabolismo , Hipotálamo Posterior/citologia , Hipotálamo Posterior/metabolismo , Infusões Intraventriculares , Comportamento Materno/efeitos dos fármacos , Microinjeções , Naftiridinas , Neurônios/metabolismo , Receptores de Orexina/metabolismo , Orexinas/administração & dosagem , Orexinas/farmacologia , Área Pré-Óptica/efeitos dos fármacos , Ratos , Ratos Wistar , Estatísticas não Paramétricas , Ureia/análogos & derivados , Ureia/farmacologiaRESUMO
Olfactory information modulates innate and social behaviors in rodents and other species. Studies have shown that the medial nucleus of the amygdala (MEA) and the ventral premammillary nucleus (PMV) are recruited by conspecific odor stimulation. However, the chemical identity of these neurons is not determined. We exposed sexually inexperienced male rats to female or male odors and assessed Fos immunoreactivity (Fos-ir) in neurons expressing NADPH diaphorase activity (NADPHd, a nitric oxide synthase), neuropeptide urocortin 3, or glutamic acid decarboxylase mRNA (GAD-67, a GABA-synthesizing enzyme) in the MEA and PMV. Male and female odors elicited Fos-ir in the MEA and PMV neurons, but the number of Fos-immunoreactive neurons was higher following female odor exposure, in both nuclei. We found no difference in odor induced Fos-ir in the MEA and PMV comparing fed and fasted animals. In the MEA, NADPHd neurons colocalized Fos-ir only in response to female odors. In addition, urocortin 3 neurons comprise a distinct population and they do not express Fos-ir after conspecific odor stimulation. We found that 80% of neurons activated by male odors coexpressed GAD-67 mRNA. Following female odor, 50% of Fos neurons coexpressed GAD-67 mRNA. The PMV expresses very little GAD-67, and virtually no colocalization with Fos was observed. We found intense NADPHd activity in PMV neurons, some of which coexpressed Fos-ir after exposure to both odors. The majority of the PMV neurons expressing NADPHd colocalized cocaine- and amphetamine-regulated transcript (CART). Our findings suggest that female and male odors engage distinct neuronal populations in the MEA, thereby inducing contextualized behavioral responses according to olfactory cues. In the PMV, NADPHd/CART neurons respond to male and female odors, suggesting a role in neuroendocrine regulation in response to olfactory cues.
Assuntos
Tonsila do Cerebelo/citologia , Hipotálamo Posterior/citologia , Neurônios/fisiologia , Odorantes , Proteínas Oncogênicas v-fos/metabolismo , Caracteres Sexuais , Animais , Jejum/fisiologia , Feminino , Regulação da Expressão Gênica/fisiologia , Glutamato Descarboxilase/genética , Glutamato Descarboxilase/metabolismo , Hipotálamo Posterior/anormalidades , Masculino , NADPH Desidrogenase/genética , NADPH Desidrogenase/metabolismo , Condutos Olfatórios/metabolismo , RNA Mensageiro/metabolismo , Ratos , Urocortinas/genética , Urocortinas/metabolismoRESUMO
Distribution and development of the melanin-concentrating hormone (MCH) system were examined by immunocytochemistry of the brain, pituitary gland and skin of the South American cichlid fish Cichlasoma dimerus. In adults, the most prominent group of MCH-ir perikarya was located in the nucleus lateralis tuberis (NLT). Outside the NLT, in the posterior hypothalamic region, a group of small neurons was found between the third ventricle and the lateral ventricular recess with delicate immunoreactive fibers that did not seem to contribute to the pituitary innervation. MCH-ir perikarya were identified at day 4 after hatching (AH) in a proliferating zone of the hypothalamic floor. Pituitary innervation could be detected at this stage. Another group of small MCH-ir neurons, only detected in pre-juvenile stages, originated close to the third ventricle in the medial hypothalamic region by day 6 AH. alphaMSH-ir neurons were localized in similar regions of the NLT and in the nucleus periventricularis posterior (NPP). Free MCH-ir neuromasts were detected in the ventral and dorsal skin of larval heads. These epidermal sensory organs were in close association with blood vessels and dermal melanocytes, suggesting that MCH synthesized in larval skin might act in an endocrine way reaching different targets and/or in a paracrine mode regulating melanin concentration in dermal melanocytes.