Orexin对蓝斑底核神经元活动的调控作用及机制研究

Orexin enhances firing activities of neurons in neonatal rat sublaterodorsal tegmental nucleus

目的研究orexin对蓝斑底核(sublaterodorsal tegmental nucleus,SLD)神经元的调控作用及其机制,初步探讨orexin对SLD神经元放电活动的影响以及在其介导的快速眼动(rapid eye movement,REM)睡眠调控中可能发挥的作用。方法采用vglut1、GAD 67、orexin-1/2型受体以及NeuN对SLD脑区进行免疫荧光染色,对SLD神经元的形态学基础进行初步研究;采用出生后8~14 d的SPF级SD大鼠,制备包含SLD脑区且具有生理活性的离体脑片,采用全细胞膜片钳记录结合神经药理学的方法来研究orexin对SLD神经元的调控作用及机制。结果SLD脑区大多数神经元均表现为vglut1和orexin-1/2型受体阳性;orexin在SLD神经元上引起了明显的去极化反应(P<0.01)并伴随SLD神经元膜电位阈下振荡的增强(P<0.05);orexin主要增强了SLD神经元膜电位在delta(P<0.05)和theta(P<0.05)频段阈下振荡的功率;orexin使SLD神经元的放电与delta频段振荡的锁相关系提前(P<0.05),并使神经元更容易放电;orexin使SLD神经元膜电位在theta频段的阈下振荡更加规则和稳定(P<0.05),从而稳定SLD神经元的放电。结论Orexin一方面通过提高SLD神经元的兴奋性,另一方面通过调控SLD神经元膜电位的阈下振荡使得SLD神经元的放电更加高效稳定,进而调控SLD神经元的活动并可能参与其介导的REM睡眠调控。

Objective To investigate the effect and underlying mechanism of orexin in modulating the firing activties of sublaterodorsal tegmental nucleus(SLD)neurons and its possible role in mediating rapid eye movement(REM)sleep regulation.Methods Immunostaining for vglut1,GAD 67,orexin-1/2 receptors and NeuN was performed on brain slices of male adult rats to characterize the distribution pattern of orexin signaling machineries in the SLD.Whole-cell patch-clamp recordings were conducted to investigate the modulatory effect of orexin on membrane potential level and sub-threshold membrane potential oscillations of SLD neurons in brain slices from neonatal SD rats(8~14 d old),and the contribution of these orexin-elicited modulations to the firing activities of SLD neurons was analyzed.Results Immunostaining results showed that the vast majority of SLD neurons were positive for vglut1 and orexin-1/2 receptors.In current-clamp configurations,orexin elicited obvious depolarization in the membrane potential(P<0.01)and increased the delta(1~4 Hz,P<0.05)and theta(4~12 Hz,P<0.05)band power in sub-threshold membrane potentialoscillations of SLD neurons.The locking phase of SLD neuronal spikes was pre-shifted in sub-threshold delta oscillations(P<0.05),and the stability of sub-threshold theta oscillation increased significantly in the presence of orexin(P<0.05),resulting in enhanced firing activities of SLD neurons.Conclusion Orexin enhances the firing activities of SLD neurons by eliciting the depolarization of the membrane potential and modulating the sub-threshold membrane oscillations of the neurons,and thus plays a role in REM sleep regulation.