Centre for Research in Neuroscience, Research Institute of the McGill University Health Center, Montreal, Quebec, Canada.
Nat Neurosci. 2010 Apr;13(4):467-74. doi: 10.1038/nn.2503. Epub 2010 Feb 28.
Osmoregulated vasopressin release is facilitated during the late sleep period (LSP) to prevent dehydration and enuresis. Previous work has shown that clock neurons in the suprachiasmatic nucleus (SCN) have low firing rates during the LSP, but it is not known how this reduced activity enhances vasopressin release. We found that synaptic excitation of rat supraoptic nucleus neurons by osmosensory afferents is facilitated during the LSP. Stimulation of the SCN at this time inhibited excitatory synaptic currents induced in supraoptic neurons by activation of osmosensory afferents. This effect was associated with an increased rate of synaptic failures and occurred without changes in frequency facilitation, quantal size or in the ratio of postsynaptic responses mediated by AMPA and NMDA receptors. We conclude that clock neurons mediate an activity-dependent presynaptic silencing of osmosensory afferent synapses onto vasopressin neurons and that osmoregulatory gain is enhanced by removal of this effect during late sleep.
渗透压调节性血管加压素释放有助于在睡眠后期（LSP）防止脱水和遗尿。先前的工作表明，视交叉上核（SCN）中的时钟神经元在 LSP 期间的放电频率较低，但尚不清楚这种活动减少如何增强血管加压素释放。我们发现，渗透压感觉传入在 LSP 期间促进大鼠视上核神经元的突触兴奋。此时刺激 SCN 抑制了渗透压感觉传入激活诱导的视上核神经元的兴奋性突触电流。这种效应与突触失败率的增加有关，而不改变频率易化、量子大小或由 AMPA 和 NMDA 受体介导的突触后反应的比值。我们得出的结论是，时钟神经元介导渗透压感觉传入到血管加压素神经元的突触活动依赖性沉默，并且在睡眠后期去除这种作用可增强渗透压调节增益。
