Lo F S, Erzurumlu R S
Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
J Neurophysiol. 2001 Mar;85(3):1088-96. doi: 10.1152/jn.2001.85.3.1088.
In the brain stem trigeminal complex of rats and mice, presynaptic afferent arbors and postsynaptic target cells form discrete modules ("barrelettes"), the arrangement of which duplicates the patterned distribution of whiskers and sinus hairs on the ipsilateral snout. Within the barrelette region of the nucleus principalis of the trigeminal nerve (PrV), neurons participating in barrelettes and those with dendritic spans covering multiple barrelettes (interbarrelette neurons) can be identified by their morphological and electrophysiological characteristics as early as postnatal day 1. Barrelette cells have focal dendritic processes, are characterized by a transient K(+) conductance (I(A)), whereas interbarrelette cells with larger soma and extensive dendritic fields characteristically exhibit low-threshold T-type Ca(2+) spikes (LTS). In this study, we surveyed membrane properties of barrelette and interbarrelette neurons during and after consolidation of barrelettes in the PrV and effects of peripheral deafferentation on these properties. During postnatal development (PND1-13), there were no changes in the resting potential, composition of active conductances and Na(+) spikes of both barrelette and interbarrelette cells. The only notable changes were a decline in input resistance and a slight increase in the amplitude of LTS. The infraorbital (IO) branch of the trigeminal nerve provides the sole afferent input source to the whisker pad. IO nerve transection at birth abolishes barrelette formation as well as whisker-related neuronal patterns all the way to the neocortex. Surprisingly this procedure had no effect on membrane properties of PrV neurons. The results of the present study demonstrate that distinct membrane properties of barrelette and interbarrelette cells are maintained even in the absence of input from the whiskers during the critical period of pattern formation.
在大鼠和小鼠的脑干三叉神经复合体中，突触前传入纤维分支和突触后靶细胞形成离散的模块（“小桶”），其排列方式与同侧口鼻部触须和鼻窦毛的模式分布一致。在三叉神经主核（PrV）的小桶区域内，参与小桶形成的神经元以及树突跨度覆盖多个小桶的神经元（桶间神经元），早在出生后第1天就可以通过它们的形态和电生理特征来识别。小桶细胞具有局灶性树突突起，其特征是存在瞬时钾离子电导（I(A)），而桶间细胞具有较大的胞体和广泛的树突野，其特征是表现出低阈值T型钙尖峰（LTS）。在本研究中，我们观察了PrV中小桶巩固期间和之后小桶神经元和桶间神经元的膜特性，以及外周去传入对这些特性的影响。在出生后发育阶段（出生后第1 - 13天），小桶神经元和桶间细胞的静息电位、主动电导组成和钠离子尖峰均无变化。唯一显著的变化是输入电阻下降和LTS幅度略有增加。三叉神经眶下（IO）分支为触须垫提供唯一的传入输入源。出生时切断IO神经会消除小桶形成以及一直到新皮层的与触须相关的神经元模式。令人惊讶的是，这个操作对PrV神经元的膜特性没有影响。本研究结果表明，即使在模式形成的关键期没有触须的输入，小桶细胞和桶间细胞独特的膜特性仍得以维持。
