Hermanstyne Tracey O, Simms Carrie L, Carrasquillo Yarimar, Herzog Erik D, Nerbonne Jeanne M
Departments of Developmental Biology and Medicine, Washington University School of Medicine, Saint Louis, MO.
Department of Biology, Washington University, St. Louis, MO.
J Biol Rhythms. 2016 Feb;31(1):57-67. doi: 10.1177/0748730415619745. Epub 2015 Dec 27.
The suprachiasmatic nucleus (SCN) regulates daily rhythms in physiology and behavior. Previous studies suggest a critical role for neurons expressing vasoactive intestinal peptide (VIP) in coordinating rhythmicity and synchronization in the SCN. Here we examined the firing properties of VIP-expressing SCN neurons in acute brain slices. Active and passive membrane properties were measured in VIP and in non-VIP neurons during the day and at night. Current-clamp recordings revealed that both VIP and non-VIP neurons were spontaneously active, with higher firing rates during the day than at night. Average firing frequencies, however, were higher in VIP neurons (3.1 ± 0.2 Hz, day and 2.4 ± 0.2 Hz, night) than in non-VIP neurons (1.8 ± 0.2 Hz, day and 0.9 ± 0.2 Hz, night), both day and night. The waveforms of individual action potentials in VIP and non-VIP neurons were also distinct. Action potential durations (APD50) were shorter in VIP neurons (3.6 ± 0.1 ms, day and 2.9 ± 0.1 ms, night) than in non-VIP neurons (4.4 ± 0.3 ms, day and 3.5 ± 0.2 ms, night) throughout the light-dark cycle. In addition, afterhyperpolarization (AHP) amplitudes were larger in VIP neurons (21 ± 0.8 mV, day and 24.9 ± 0.9 mV, night) than in non-VIP neurons (17.2 ± 1.1 mV, day and 20.5 ± 1.2 mV, night) during the day and at night. Furthermore, significant day/night differences were observed in APD50 and AHP amplitudes in both VIP and non-VIP SCN neurons, consistent with rhythmic changes in ionic conductances that contribute to shaping the firing properties of both cell types. The higher day and night firing rates of VIP neurons likely contribute to synchronizing electrical activity in the SCN.
视交叉上核（SCN）调节生理和行为的日常节律。先前的研究表明，表达血管活性肠肽（VIP）的神经元在协调SCN的节律性和同步性方面起着关键作用。在此，我们研究了急性脑片中表达VIP的SCN神经元的放电特性。在白天和夜间测量了VIP神经元和非VIP神经元的主动和被动膜特性。电流钳记录显示，VIP神经元和非VIP神经元均具有自发活动，白天的放电频率高于夜间。然而，无论是白天还是夜间，VIP神经元的平均放电频率（白天为3.1±0.2Hz，夜间为2.4±0.2Hz）均高于非VIP神经元（白天为1.8±0.2Hz，夜间为0.9±0.2Hz）。VIP神经元和非VIP神经元的单个动作电位波形也不同。在整个明暗周期中，VIP神经元的动作电位持续时间（APD50）（白天为3.6±0.1ms，夜间为2.9±0.1ms）比非VIP神经元（白天为4.4±0.3ms，夜间为3.5±0.2ms）短。此外，白天和夜间VIP神经元的超极化后电位（AHP）幅度（白天为21±0.8mV，夜间为24.9±0.9mV）均大于非VIP神经元（白天为17.2±1.1mV，夜间为20.5±1.2mV）。此外，在VIP和非VIP SCN神经元的APD50和AHP幅度中均观察到显著的昼夜差异，这与离子电导的节律性变化一致，这些变化有助于塑造两种细胞类型的放电特性。VIP神经元白天和夜间较高的放电频率可能有助于同步SCN中的电活动。
