Twenty-four hour rhythms of the hypothalamic CRF production and release, and the afferent pathways from the light- and food-entrainable circadian oscillations.

本研究的目的是阐明光和食物刺激的昼夜节律振荡对下丘脑CRF神经元的传入途径，CRF神经元在下丘脑-垂体-肾上腺皮质轴的调节中起关键作用。自由采食条件下大鼠表现为光敏感性昼夜节律，而限制采食条件下表现为食物敏感性昼夜节律，两种条件下室旁核（PVN）和正中隆起（ME）中CRF的浓度昼夜变化。自由采食条件下，CRF浓度在光照早期较高，在黑暗早期较低。另一方面，CRF浓度在每日进餐前较低，在进餐后升高。这些结果表明，食物敏感的昼夜节律振荡不仅表现在内侧核，而且也表现在室旁核的CRF神经元的功能上。 ...更多信息 为研究食物诱发振荡的传入通路，将各种神经毒剂微量注射到脑内的几个区域。其中，6-羟基多巴胺（6-OHDA）进入PVN或进入中脑的儿茶酚胺能神经元的上行束取消食物耐受性的昼夜皮质酮节律，为了更好地了解食物耐受性的CRF节律中的儿茶酚胺能神经元的作用，在体微透析的方法，连续监测PVN中的去甲肾上腺素。因此，PVN中的去甲肾上腺素在每日餐前增加，餐后减少。这一发现与6-OHDA效应一起提示去甲肾上腺素促进了进食前CRF的释放，在支配PVN的上行儿茶酚胺能神经元中，神经肽Y（NPY）与去甲肾上腺素共存。餐后室旁核NPY含量增加，提示NPY释放终止。NPY与去甲肾上腺素对CRF释放的协同作用是最合理的。少

The purpose of the present study is to clarify the afferent pathways from the lightand food-entrainable circadian oscillations to the hypothalamic CRF neurons which play a key role in the regulation of the hypothalamus-pitultary-adrenocortical axis. The light-entrainable circadian rhythm is expressed in rats under ad libitum feeding, while the food-entrainable circadian rhythm become apparent under restricted feeding.The CRF concentrations in the paraventricular nucleus(PVN)where CRF is produced, and in the median eminence(ME)where CRF is released varied around the clock under both feeding conditions. The CRF concentration is high in the early light period and low in the early dark period under ad libitum feeding. On the other hand, the CRF concentration is low prior to the time of daily meal and increases after meal supply. The findings indicate that the food-entrainable circadian oscillation manifests itself on the functions of the CRF neurons In the PVN as well as in the ME.To clari … More fy the afferent pathway from the food-entrainable oscillation, various neurotoxic agents were microinjected into several areas In the brain. Among them, 6hydroxydopamine(6-OHDA)into the PVN or into the ascending bundle of catecholaminergic neurons in the midbrain abolished the food-entrainable circadian corticosterone rhythm.To have better understanding of the role of catecholaminergic neurons in the food-entrainable CRF rhythm, noradrenaline in the PVN was continuously monitored by means of in vivo microdialysis. As a result, noradrenaline In the PVN Increased prior to the daily meal and decreased after meal supply. The finding suggests, together with the 6-OHDA effect, that noradrenaline accelerates the pre-feeding CRF release.Neuropeptide Y(NPY)coexists with noradrenaline in the ascending catecholaminergic neurons which innervate the PVN. NPY in the PVN increased after the daily meal, which suggests the termination of NPY release. The synergistic action of NPY with noradrenaline on CRF release is most plausible. Less