RESUMO
Melatonin has been shown to regulate several immune functions, and some authors showed that leukocytes are also able to produce the indolamine. In fact, it seems to take part in some immunoregulatory axis, including that related to interferon (IFN) production. So, we evaluated the rate of tryptophan consumption and melatonin and serotonin production in peritoneal cavity-isolated macrophages and the effect of IFN-alpha and -gamma, lipopolysaccharide (LPS), and phorbol myristate acetate (PMA) on such parameters. Our results indicate that macrophages obtained from the peritoneal cavity of normal rats when incubated with tryptophan show an increase in arylalkylamine N-acetyltransferase activity that corresponds to an increased melatonin production, as determined in the incubation medium. This process is regulated by IFN-alpha and -gamma, PMA, LPS, and the serum from tumor-bearing rats, opening the possibility of speculation about different immunoregulatory loops acting through the balance of melatonin/serotonin production by such cells.
Assuntos
Macrófagos Peritoneais/efeitos dos fármacos , Melatonina/biossíntese , Serotonina/biossíntese , Triptofano/farmacologia , Animais , Antineoplásicos/farmacologia , Arilamina N-Acetiltransferase/metabolismo , Carcinógenos/farmacologia , Interferon-alfa/farmacologia , Interferon gama/farmacologia , Lipopolissacarídeos/farmacologia , Macrófagos Peritoneais/metabolismo , Masculino , Cavidade Peritoneal/citologia , Radioimunoensaio , Ratos , Ratos Wistar , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
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
It has been shown that the basal retrochiasmatic area (RCHb), situated immediately ventral to the third ventricle behind the suprachiasmatic nucleus and in front of the arcuate nucleus, is implicated in the nocturnal inhibitory process of melatonin production induced by short-term retinal photo-stimulation. In the present study, the projections of the RCHb have been examined using the Phaseolus vulgaris leucoagglutinin (PHA-L) method in the rat. Considering the putative role of the RCHb in contributing to the short-term photo-inhibition of the pineal gland during the night, it is reasonable to suppose that the RCHb may ultimately inhibit the sympathetic outflow of the upper thoracic segments, known to be critically involved in the control of melatonin secretion. Of particular interest, the present anterograde tract-tracing study indicates all possible paths from the RCHb which may conceivably be involved in influencing the sympathetic outflow and, therefore, melatonin production. Thus, apart from a direct projection to the intermediolateral column at thoracic levels of the spinal cord, the RCHb is in a position to control the sympathetic outflow through other potential routes, such as the dorsal parvicellular part of the paraventricular nucleus of the hypothalamus, lateral hypothalamic area, ventromedial nucleus of the hypothalamus, lateral part of the periaqueductal gray and Barrington's nucleus.
Assuntos
Mapeamento Encefálico , Quiasma Óptico/fisiologia , Glândula Pineal/metabolismo , Vias Visuais/fisiologia , Animais , Estimulação Luminosa , Fito-Hemaglutininas , RatosRESUMO
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
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.