RESUMO
The present study attempted to characterize the effects of electrolytic lesions of the hypothalamic dorsomedial nucleus on the daily profile of pineal metabolism as well as on the inhibition of pineal melatonin synthesis induced by acute light exposure during the night. Adult male Wistar rats (n = 107, 12:12 h light-dark cycle) were left intact (n = 47) or lesioned (n = 60). Lesioned rats and their respective controls were killed at six time points distributed throughout the light-dark cycle. At ZT (zeitgeber time) 18 the animals were killed either in the dark or after 15 min of light stimulation. Pineal glands were assayed using high-performance liquid chromatography with electrochemical detection (HPLC-ED). There was no difference in the amounts of pineal indoles between lesioned and control rats under any of the experimental situations tested. These results suggest that in rats, the hypothalamic dorsomedial nucleus does not participate in either the neural control of daily pineal metabolism or the nocturnal light-induced inhibition of the pineal metabolism.
Assuntos
Núcleo Hipotalâmico Dorsomedial/fisiologia , Glândula Pineal/metabolismo , Serotonina/análogos & derivados , 5-Hidroxitriptofano/metabolismo , Animais , Cromatografia Líquida de Alta Pressão , Núcleo Hipotalâmico Dorsomedial/cirurgia , Eletrocirurgia , Ácido Hidroxi-Indolacético/metabolismo , Hipotálamo/fisiologia , Hipotálamo/cirurgia , Luz , Masculino , Melatonina/biossíntese , Ratos , Ratos Wistar , Serotonina/metabolismo , Triptofano/metabolismoRESUMO
The aim of the present investigation was to study the effect of neurotoxic ibotenic acid lesion of the retrochiasmatic area on the daily profile of pineal N-acetylserotonin and melatonin synthesis and on the pineal metabolic reactivity to nocturnal short-term retinal photostimulation. Groups of rats were killed 6 h after lights off either in the dark of immediately after being photostimulated for 1 or 15 min. Additionally, groups of rats were sacrificed at six different time points throughout the 24-hour light-dark cycle. The results suggested the presence of two functionally distinct territories in the retrochiasmatic area. The basal retrochiasmatic area, an area situated immediately ventral to the third ventricle, behind the suprachiasmatic nuclei and in front of the arcuate nucleus, is implicated in the nocturnal inhibitory process induced by short-term retinal photostimulation. The lateral retrochiasmatic area, which is situated immediately lateral to the anterior periventricular nucleus, below the anterior hypothalamic nucleus and in front of the ventromedial hypothalamic nucleus, is importantly involved in the control of the peak amplitude of the daily production of N-acetylserotonin and melatonin by the pineal gland.
Assuntos
Ácido Ibotênico/farmacologia , Glândula Pineal/metabolismo , Núcleo Supraquiasmático/fisiologia , Animais , Antagonistas de Aminoácidos Excitatórios/farmacologia , Luz , Masculino , Melatonina/biossíntese , Ratos , Ratos Wistar , Retina/fisiologia , Serotonina/análogos & derivados , Serotonina/biossíntese , Núcleo Supraquiasmático/efeitos dos fármacosRESUMO
Although the pineal gland influences several physiological systems, only a few studies have investigated its role in the intermediary metabolism. In the present study, male Wistar rats, pinealectomized or sham-operated 6 wk before the experiment, were submitted to both intravenous glucose tolerance tests (IVGTT) and insulin binding as well as glucose transport assays in isolated adipocytes. The insulin receptor tyrosine kinase activity was assessed in liver and muscle. The insulin secretory response during the IVGTT was impaired, particularly in the afternoon, and the glucose transport responsiveness was 33% lower in pinealectomized rats. However, no difference was observed in the insulin receptor number of adipocytes between groups as well as in insulin-stimulated tyrosine kinase activity, indicating that the initial steps in the insulin signaling were well conserved. Conversely, a 40% reduction in adipose tissue GLUT-4 content was detected. In conclusion, pinealectomy is responsible for both impaired insulin secretion and action, emphasizing the influence of the pineal gland on glucose metabolism.
Assuntos
Intolerância à Glucose/etiologia , Hipoglicemiantes/farmacologia , Insulina/farmacologia , Proteínas Musculares , Glândula Pineal/fisiologia , Tecido Adiposo/citologia , Tecido Adiposo/efeitos dos fármacos , Animais , Transporte Biológico/fisiologia , Desoxiglucose/farmacocinética , Glucose/metabolismo , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 4 , Insulina/metabolismo , Fígado/enzimologia , Masculino , Proteínas de Transporte de Monossacarídeos/metabolismo , Músculo Esquelético/enzimologia , Ratos , Ratos Wistar , Receptores Proteína Tirosina Quinases/metabolismo , Receptor de Insulina/metabolismoRESUMO
Melatonin is the main hormone involved in the neuroendocrine-immune axis. It also presents antitumour activity. To evaluate the role of melatonin on the progression of Walker-256 tumour in rats we determined the effect of the hormone on some biochemical and functional aspects of macrophage and lymphocytes from cachectic rats. An important finding observed in immune cells from tumour-bearing (TB) rats is the impairment on glutamine and glucose metabolism in such cells. These changes are very similar to those observed in pinealectomized rats (PNX). The increased production of lactate and the flux of glucose through the Krebs cycle and the reduction in glutamine consumption seems to be involved in the immunosuppression presented in the TB and PNX animals. Melatonin treatment restored the changes observed in the metabolism of glucose and glutamine and stimulated the proliferation of lymphocytes from tumour-bearing rats. The results indicate that the effect of melatonin upon tumour growth involves the stimulation of the immune system by the hormone.
Assuntos
Antioxidantes/farmacologia , Carcinoma 256 de Walker/imunologia , Linfócitos/enzimologia , Macrófagos/enzimologia , Melatonina/farmacologia , Animais , Dióxido de Carbono/metabolismo , Radioisótopos de Carbono , Citrato (si)-Sintase/metabolismo , Ciclo do Ácido Cítrico/fisiologia , Glucose/metabolismo , Glucosefosfato Desidrogenase/metabolismo , Glutaminase/metabolismo , Glutamina/metabolismo , Hexoquinase/metabolismo , Linfócitos/imunologia , Macrófagos/imunologia , Masculino , Glândula Pineal/cirurgia , Ratos , Ratos WistarRESUMO
Melatonin is the main hormone involved in the neuroendocrine-immune axis. It also presents antitumour activity. To evaluate the role of melatonin on the progression of Walker-256 tumour in rats we determined the effect of the hormone on some biochemical and functional aspects of macrophage and lymphocytes from cachectic rats. An important finding observed in immune cells from tumour-bearing (TB) rats is the impairment on glutamine and glucose metabolism in such cells. These changes are very similar to those observed in pinealectomized rats (PNX). The increased production of lactate and the flux of glucose through the Krebs cycle and the reduction in glutamine consumption seems to be involved in the immunosuppression presented in the TB and PNX animals. Melatonin treatment restored the changes observed in the metabolism of glucose and glutamine and stimulated the proliferation of lymphocytes from tumour-bearing rats. The results indicate that the effect of melatonin upon tumour growth involves the stimulation of the immune system by the hormone.
RESUMO
The aim of the present work was to test the pineal gland metabolic reactivity to nocturnal retinal short term photic stimulation in superior cervical ganglionectomized rats. The experimental support for this work is the appearance of a transitory post synaptic hyperactivity in the pineal gland, during the anterograde degenerating process of the conarii sympathetic nerve fibers after surgical removal of the cell body. In this situation the pineal gland is deafferented from the peripheral sympathetic nervous system keeping intact, however, the direct central connections to the deep pineal/lamina intercalaris region (DP). The results show a blockade of the pineal noradrenergic stimulatory process due to the retinal photostimulation. The inactivation of N-acetyltransferase led to a true metabolic shift to the oxidative pathway resulting in a decrease of the amount of N-acetylserotonin and an increase of the amount of serotonin, 5-hydroxyindoleacetic acid and 5-hydroxytryptophan. This inhibitory process brought into action by retinal illumination is dependent on the direct central neural connections to the pineal gland, since rats that were lesioned in the DP, previously to ganglionectomy, did not show any alteration on the indolic content of the pineal gland when subjected to nocturnal retinal photostimulation.
Assuntos
Ganglionectomia , Glândula Pineal/metabolismo , Retina/fisiologia , 5-Hidroxitriptofano/análise , 5-Hidroxitriptofano/metabolismo , Animais , Escuridão , Eletrofisiologia , Ácido Hidroxi-Indolacético/análise , Ácido Hidroxi-Indolacético/metabolismo , Luz , Masculino , Estimulação Luminosa , Glândula Pineal/química , Ratos , Ratos Wistar , Serotonina/análogos & derivados , Serotonina/análise , Serotonina/metabolismo , Gânglio Cervical Superior/cirurgia , Triptofano/análise , Triptofano/metabolismo , Vias Visuais/fisiologiaRESUMO
The aim of the present work was to study, in rats, the effects of lesions of the thalamic intergeniculate leaflet (IGL) and the deep pineal/lamina intercalaris region (DP) on the diurnal profile of N-acetylserotonin (NAS) and on the nocturnal pineal reactivity to acute retinal light stimulation (1 or 15 min). The 24-h experiment shows that there is no phase-shifting on the diurnal NAS curve of groups of rats with bilateral IGL lesion compared to the controls. On the other hand there is a significant reduction on the amplitude of pineal NAS content observed in every nocturnal point of the curve. The pineal glands of IGL-lesioned rats, after 1 min of retinal light stimulation, keep their NAS content equal to the lesioned dark-killed rats. Nonetheless, after 15 min of photostimulation, the pineal NAS content is reduced to nearly zero equally to the control animals. DP lesion does not modify the content of NAS in the pineal gland of rats killed in the dark. However, the pineal photo-inhibition process induced by 1 min of light exposure is impaired. These results suggest that: (1) the intergeniculate leaflet has a role in regulating the amplitude of the diurnal rhythm of pineal NAS production rather than its phase entrainment to light-dark cycle. This effect is not dependent on the direct geniculo-pineal connections. (2) The nocturnal pineal photo-inhibition phenomenon could be decomposed in two processes. One, triggered by short pulses of light and totally dependent on the IGL and partially dependent on the direct monosynaptic pathway between this structure and the pineal gland.(ABSTRACT TRUNCATED AT 250 WORDS)