Coupling of suprachiasmatic neuronal activity and peptide rhythms : pacemaker structures

本实验旨在阐明视交叉上核（SCN）中振荡神经元的耦合机制，使起搏器在各种生理功能中驱动单一稳定的昼夜节律。时钟基因表达节律：通过原位杂交检测时钟基因Clock和BMAL1的表达。Clock和BMAL1在SCN中以昼夜节律方式强烈表达，节律180度异相。在不同昼夜时间给予30min光脉冲后，BMAL1的表达在所有检测阶段都增加，而Clock的表达则依赖于相位。这两个基因可能分别在光携射中起参数和非参数两种作用中的一种。SCN切片中的AVP和VIP节律：在插入培养膜上培养的SCN切片显示AVP节律强劲，并逐渐转变为母体AVP节律和VIP节律不同步，但两种节律在培养过程中减弱。结果表明，AVP和VIP是由不同的振荡器驱动的，在培养过程中它们是不同步的。神经元振荡与肽节律产生的耦合：在多电极培养皿上培养单个SCN神经元，比较其昼夜放电节律和肽节律。只有在神经元节律同步的培养皿中才检测到显著的昼夜肽节律，这表明肽节律反映了细胞振荡的耦合性。单个SCN神经元振荡器的突触耦合：通过检查具有同步昼夜节律和非同步节律的一对SCN神经元的峰值的相互关系，研究了功能性突触在细胞振荡耦合中的作用。结果表明，短突触延迟的兴奋性突触相互作用使SCN内的昼夜节律放电振荡神经元同步。

Present experiment was undertaken to clarify the coupling mechanisms of oscillatory neurons in the suprachiasmatic nucleus (SCN) which enables the pacemaker to drive a single stable circadian rhythm in the various physiological functions.1. Clock gene expression rhythms : Expression of clock genes, Clock and BMAL1, was examined by in situ hybridization. Clock and BMAL1 are strongly expressed in the SCN with a circadian fashion and the rhythms were 180 degree out of phase. To a 30 min light pulse given at various circadian times, BMAL1 expression was increased at all phases examined, while that of Clock, phase-dependently. The two genes may separately play one of the two roles in the light entrainment, parametric and non-parametric.2. AVP and VIP rhythms in the SCN slice : SCN slices cultured on a culture-insert membrane showed robust rhythms in AVP which phased to maternal AVP rhythm and desynchronized rhythms in VIP, but both rhythms damped out during the culture. The results suggest that AVP and VIP are driven by separate oscillators which are desynchronized during the culture.3. Coupling of neuronal oscillation and peptide rhythm generation : Single SCN neurons were cultured on a multi-electrode dish, and the circadian firing rhythms and peptide rhythms were compared. Significant circadian peptide rhythms were detected only in cultured dishes with synchronized neuronal rhythms, suggesting the peptide rhythm reflects the coupling of cellular oscillations.4. Synaptic coupling of individual SCN neuronal oscillator : The role of functional synapses in the coupling of cellular oscillations was studied by examining cross-correlation of spikes of a pair of SCN neurons which showed synchronized circadian firing rhythms and that with desynchronized rhythms. The result showed that an excitatory synaptic interaction with a short synaptic delay synchronizes the circadian firing rhythm oscillating neurons in the SCN.