大鼠腦中側臂旁核區神經細胞電生理特性之探討

Abstract

臂旁核（Parabrachial Nucleus）一般被認為與自律神經系統訊號的傳遞有關，對於腸胃道、臟器功能及痛覺的調控扮演著相當重要的角色。臂旁核又分為中臂旁核（Medial Parabrachial Nucleus, MPB）及側臂旁核（Lateral Parabrachial Nucleus, LPB），先前研究發現側臂旁核的神經軸突似乎有一部分會投射到橋腦的Ａ７正腎上腺素細胞群中，但對於側臂旁核的神經細胞組成及特性還未有清楚的研究，所以我們想要研究側臂旁核區神經細胞的電生理特性，試著對這些細胞作分類，並嚐試找出投射到Ａ７核區的細胞群。 我們先量測細胞的自發性放電反應，並給予適當的電刺激流程，記錄細胞放電的電訊號特徵。根據延遲放電與否和是否有過極化時的袋狀膜電位凹陷,記錄的細胞可分為四大類。結果顯示，這四群細胞在動作電位振幅、膜電阻及半波寬(Spike Half Width)的特性上並沒有顯著的差異，但在能引起動作電位的電流閾值(Rheobase)大小的項目上，各組之間均有顯著的差異。在自發性放電反應的記錄中，各細胞群內皆包含不會自發性放電、會規律自發性放電、會不規律自發性放電等三種細胞。 在細胞形態的部分，我們發現會延遲放電且有過極化時的袋狀膜電位凹陷的這一組，其細胞突起分布較為局部，而其他組別則有較長遠的分布，有機會投射到Ａ７核區，且這些細胞多分布於側臂旁核的中側(medial)近前端。

Parabrachial nucleus (PBN) is involved in transmission of autonomic information. It is an important site for both visceral and gustatory afferent processing. It is also involved in the pain regulation of the descending pain pathway. The PBN has traditionally been separated into lateral (LPBN) and medial (MPBN), and a part of axons of LPB neuron seem to project to the NAergic A7 nucleus, which contains a group of noradrenergic cells and locates in the pons. However, the composition and electro-physiological characteristics were still unknown. Here, we study the intrinsic membrane characteristics of LPB neurons and try to separate these cells. First we record the spontaneous firing pattern of LPB neurons, and then give different stimulation protocols to record their intrinsic property. The cells we record can be grouped into four categories by the criteria of the delay onset and the hyperpolarizing voltage sag. Among these four groups, there are no significant differences in resting membrane potential, spike amplitude and spike half-width. However,the difference of the rheobase are significant in every pair of group. Comparing the spontaneous firing pattern, cells in all groups contain all the firing patterns, include regular-spontaneous firing pattern, non-regular-spontaneous firing pattern and non-spontaneous firing pattern. In comparison of morphology, the neuron processes of the group that showed the prominent delay onset and the hyperpolarizing voltage sag spreaded locally, while other groups had longer ones and spread more close to the A7 nucleus.