Roles of light and serotonin in the regulation of gastrin-releasing peptide and arginine vasopressin output in the hamster SCN circadian clock.
Roles of light and serotonin in the regulation of gastrin-releasing peptide and arginine vasopressin output in the hamster SCN circadian clock.
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DOI：
10.1111/j.1460-9568.2010.07374.x
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发表时间：
2010-10
期刊：
影响因子：
--
通讯作者：
Glass JD
中科院分区：
文献类型：
--
作者：
Francl JM;Kaur G;Glass JD
哺乳动物视交叉上核（SCN）昼夜节律钟的每日定时是由来自视网膜的光输入通过视网膜下丘脑束调节的。该信号传导由谷氨酸介导，谷氨酸激活SCN视网膜受体单位，其部分通过释放胃泌素释放肽（GRP）与起搏细胞通信。SCN的传出信号涉及另一种含SCN的肽，精氨酸加压素（AVP）。值得注意的是，关于调节这些肽的机制知之甚少，因为关于SCN中体内肽释放的文献很少。在这里，微透析放射免疫分析程序被用来表征机制控制GRP和AVP释放仓鼠SCN。在14小时：10小时24小时LD循环下饲养的动物中，两种肽均表现出每日释放的波动，早晨水平增加，中午左右达到峰值。在恒定的黑暗下，AVP持续这种模式，但GRP的节律性改变，其特征在于整个主观夜间和主观白天早期的广泛高原。神经元释放的肽证实了他们的抑制与反微透析灌注钙阻滞剂和刺激去极化剂。用5-HT 1A，7激动剂，8-OH-DPAT进行反向微透析灌注，在白天显著抑制GRP，但对AVP影响不大。此外，灌流与谷氨酸激动剂NMDA，或暴露于光在夜间，增加GRP，但不影响AVP。这些分析揭示了SCN肽能活性的不同的每日节律，GRP而不是AVP释放通过抑制光相位重置的β-肾上腺素能激活而衰减，并且通过介导该相位重置的β-肾上腺素能和光刺激而激活。
Daily timing of the mammalian circadian clock of the suprachiasmatic nucleus (SCN) is regulated by photic input from the retina via the retinohypothalamic tract. This signaling is mediated by glutamate which activates SCN retinorecipient units communicating to pacemaker cells in part through the release of gastrin-releasing peptide (GRP). Efferent signaling from the SCN involves another SCN-containing peptide, arginine vasopressin (AVP). It is notable that little is known concerning the mechanisms regulating these peptides, as literature on in vivo peptide release in the SCN is sparse. Here, microdialysis-radioimmunoassay procedures were used to characterize mechanisms controlling GRP and AVP release in the hamster SCN. In animals housed under a 14hr:10hr 24hr LD cycle both peptides exhibited daily fluctuations of release, with levels increasing during the morning to peak around midday. Under constant darkness, this pattern persisted for AVP, but rhythmicity was altered for GRP, characterized by a broad plateau throughout the subjective night and early subjective day. Neuronal release of the peptides was confirmed by their suppression with reverse-microdialysis perfusion of calcium blockers and stimulation with depolarizing agents. Reverse-microdialysis perfusion with the 5-HT1A,7 agonist, 8-OH-DPAT, during the day significantly suppressed GRP but had little effect on AVP. Also, perfusion with the glutamate agonist NMDA, or exposure to light at night, increased GRP but did not affect AVP. These analyses reveal distinct daily rhythms of SCN peptidergic activity, with GRP but not AVP release attenuated by serotonergic activation that inhibits photic phase-resetting, and activated by glutamatergic and photic stimulation that mediate this phase-resetting.
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