RESUMO
Significant elevation in plasma corticosterone of rats achieved by intraperitoneal (i.p.) administration of corticosterone (2.4 mg/kg) was associated with a rapid (2.5 min) and significant increase in hypothalamic histamine (HA) levels which persisted for 60 min. Midbrain and cortical HA concentrations were not affected. Significant and prolonged elevation of hypothalamic, midbrain and cortical HA levels was achieved by L-histidine administration (500 mg/kg i.p.). The most significant increase was noted in the hypothalamus and persisted for 10 hours. The elevated brain HA levels were associated with significant increase in plasma corticosterone levels which lasted for 120 mins. Present data supports the involvement of central HA in endocrine function.
Assuntos
Corticosterona/sangue , Histamina/metabolismo , Hipotálamo/metabolismo , Animais , Córtex Cerebral/metabolismo , Histidina/farmacologia , Hipotálamo/efeitos dos fármacos , Masculino , Mesencéfalo/metabolismo , Ratos , Ratos Endogâmicos , Fatores de TempoRESUMO
Exposure of rats to platform stress induced a significant elevation in hypothalamic histamine levels. Air blast-stress resulted in a significant increase in hypothalamic histamine concentration and in histidine decarboxylase activity. No significant changes were noted either in the enzyme activity or in histamine levels in the midbrain or cortex of stressed rats. In the nonstressed rats, diphenhydramine (7.5 mg/kg intragastrically), a H1-receptor antagonist, did not influence histidine decarboxylase activity or histamine concentration in any of the three brain regions investigated. However, diphenhydramine pretreatment prevented the increase in histidine decarboxylase activity induced by air blasts. In untreated rats, plasma corticosterone levels were significantly elevated following either platform stress (4.5-fold) or air blasts (7.8-fold). A significant increase was also noted in saline and diphenhydramine-treated animals following these stressors, however, the increase in saline or diphenhydramine treated rats following air blasts was significantly less than that seen in untreated stressed controls.
Assuntos
Carboxiliases/metabolismo , Corticosterona/sangue , Difenidramina/farmacologia , Histamina/metabolismo , Histidina Descarboxilase/metabolismo , Hipotálamo/efeitos dos fármacos , Estresse Fisiológico/enzimologia , Animais , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/enzimologia , Hipotálamo/enzimologia , Masculino , Mesencéfalo/efeitos dos fármacos , Mesencéfalo/enzimologia , Ratos , Ratos Endogâmicos , Receptores Histamínicos H1/efeitos dos fármacosAssuntos
Intoxicação Alcoólica/enzimologia , Encéfalo/efeitos dos fármacos , Histamina/metabolismo , Animais , Encéfalo/enzimologia , Córtex Cerebral/efeitos dos fármacos , Corticosterona/sangue , Histamina N-Metiltransferase/metabolismo , Histidina Descarboxilase/metabolismo , Humanos , Hipotálamo/efeitos dos fármacos , Masculino , Mesencéfalo/efeitos dos fármacos , Ratos , Ratos EndogâmicosRESUMO
Hypothalamic histamine exhibited circadian fluctuations in male Sprague-Dawley rats; low values were found during the dark period when spontaneous locomotor activity (S.L.A.) and temperature were elevated. A relatively high hypothalamic histamine level was observed during the early period of the light cycle and was associated with decreased S.L.A. and temperature. Histamine concentration was high when corticosterone levels were low at the end of the dark cycle and during the morning hours (4 a.m.-1 p.m.); but histamine levels were relatively constant while corticosterone concentration dropped during afternoon and early night hours (4 p.m.-10 p.m.). Furthermore, the lowest hypothalamic histamine level (at 1 a.m.) was associated with the average plasma corticosterone value, thus no consistent relationship between histamine and corticosterone levels could be observed. Circadian fluctuations in brain histamine may support its role in brain function.
Assuntos
Temperatura Corporal , Química Encefálica , Corticosterona/sangue , Histamina/metabolismo , Atividade Motora/fisiologia , Animais , Ritmo Circadiano , Hipotálamo/metabolismo , Masculino , RatosRESUMO
Exposure of rats to air blasts for 1, 5 and 15 min resulted in a significant increase in plasma corticosterone level and in the hypothalamic histamine concentration. Midbrain histamine content was increased after 1 and 5 min of exposure but cortical histamine increased following 1 min of exposure only. Stress of longer duration (30 mins did not significantly affect histamine concentration in any of the three brain regions investigated, although plasma corticosterone level remained very significantly (14.5-fold) elevated. Repeated exposure of rats to air blasts of 15 min duration resulted in a significant elevation of hypothalamic histamine concentration while midbrain and cortical histamine was not significantly altered. Plasma corticosterone level was again very significantly (10-fold) increased. Present results suggest the involvement of brain histamine in the response to stress.
Assuntos
Encéfalo/metabolismo , Histamina/metabolismo , Estresse Fisiológico/metabolismo , Movimentos do Ar , Animais , Córtex Cerebral/metabolismo , Corticosterona/sangue , Hipotálamo/metabolismo , Masculino , Mesencéfalo/metabolismo , Ratos , Estresse Fisiológico/sangue , Estresse Fisiológico/etiologiaRESUMO
Chronic morphine administration to rats resulted in a significant decrease in the hypothalamic and cerebro-cortical histamine concentrations. These low histamine values were restored to control levels when L-histidine was administered daily along with morphine treatment. Chronic treatment with L-histidine prevented the midbrain and cerebro-cortical histamine depletion in morphine-withdrawn rats, whereas in the hypothalamus the histamine level remained significantly decreased. The present data suggests that histamine may play a role in morphine dependence and withdrawal.