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大鼠中央杏仁核5--HT_(3)受体参与胸腺功能调制

徐民, 陈伟强, 王基平, Foster D JR, 许德义

东南大学基础医学院药理学教研室.江苏,南京 210009；国立南澳大学医药学院三申研究所.SAS000

摘要

该研究旨在探讨大鼠中央杏仁核（central amygdala ，CeA）内5--HT_(3)受体激动之后，对丝裂原刀豆球蛋白A（concanavalin A，ConA）刺激的胸腺细胞增殖反应的影响，及其潜在的神经内分泌调节环路。分别经大鼠腹腔（intraperitoneal，i.p.）、双侧侧脑室（intracerebroventricle，i.c.v.）和双侧ceA（intracentral amygdala,i.c.a.）注射选择性5--HT_(3)受体激动剂1-phenylbiguanide（PBG），同时制备正常大鼠胸腺细胞悬液与不同浓度PBG（1×10~(-8)---1×10~(-5)mol／L）体外共同孵育。经MTT法测定显示，无论有无ConA刺激，正常大鼠离体胸腺细胞在与PBG（1×10~(-8)---1×10~(-5)mol／L）体外共同孵育时其增殖反应均不受后者影响；PBG i.p.（每天0.5mg／kg，连续5d）对ConA刺激的胸腺细胞的增殖反应亦无影响，而PBG i.c.v.（每天10#mu#g/侧，连续5d）则显著增强之；当PBG i.c.a.（每天1.0#mu#g／侧，1d或连续3、5、7d）时，ConA刺激的胸腺细胞的增殖反应于给药后d1即开始增强且日益显著，d5达到高峰，d7则趋于减弱。在给予PBG5min前相同给药部位先给予5--HT_(3)受体拮抗剂tropisetvan（TRP）预处理可逆转PBG的促胸腺细胞增殖效应。免疫组织化学SABC法检测显示，PBG（1.0#mu#g／侧，i.c.a.）单次给药后各脑区可相继出现大量c--Fos阳性细胞（CeA：1h；海马及皮层：1---2h；下丘脑：4h；中脑导水管周围灰质：8h），并迅速达到各自高峰（CeA：1h；海马及皮层：2h；下丘脑：4h），与相应的生理盐水对照组及TRP预处理组相比均有显著性差异。随后，这一表达在各脑区中逐步减弱并消失（CeA：4h；海马、皮层及下丘脑：8h）。由此推论，大鼠CeA内5--HT_(3)受体至少可部分通过边缘系统--皮层--下丘脑--中脑导水管周围灰质这一神经内分泌环路调制胸腺细胞功能。

关键词： 5-HT_(3)受体; 1-phenylbiguanide; 中央杏仁核; 胸腺细胞; c-fos; 神经免疫调制; 大鼠

5--HT_(3) receptors in the central amygdala mediate the modulation of thymus function in rats

Xu Min, Chen Weiqiang, Wang Jiping, Foster D JR, Xu Deyi

Department of Pharmacology, School of Basic Medicine, Southeast University.Nanjing 210009,Jiangsu；Australia

Abstract

The aim of the present study was to investigate the modulatory role of activated 5-HT_(3) receptors in the central amygdala (CeA) on mitogen concanavalin A (ConA)-stimulated proliferative response of thymocytes in rats and the underlying neuroendocrine regulation circuits. 1-phenylbiguanide (PBG), a putative selective 5-HT_(3) receptor agonist, was administered by intraperitoneal (i.p.),bilateral intracerebroventriclular (i.c.v.), and bilateral intracentral amygdala (i.c.a.) injection. In addition, thymocytes isolated from untreated rats were incubated with PBG (at a range of concentrations of 1×10~(-8)--1×10~(-5) mol/L) in vitro in the presence and absence of ConA, in order to investigate any direct effect of PBG on the proliferation in vitro. MTT method was applied to demonstrate the effect of PBG on the proliferative response of thymocytes. An immunohistochemical SABC assay was used to describe the expression profiles of c-Fos-positive cells in different brain regions including the CeA, hippocampus, cortex, hypothalamus and periaqueductal gray (PAG) at 1, 2, 4 and 8 h after bilateral single-administration of PBG by i.c.a. (1.0 #mu#g/side). Results showed that PBG (1×10~(-8)--1×10~(-5) mol/L) had no significant influence on the proliferative responses of the isolated thymocytes in vitro, no matter ConA was present or not. The proliferation of thymocytes stimulated by ConA was not significantly changed when PBG was administered by i.p. (0.5 mg/kg per day, for consecutive 5 d), whereas it was remarkably enhanced after bilateral i.c.v, injection of PBG (10 μg/side per day, for consecutive 5 d). Similarly, when PBG was injected bilaterally by i.c.a. (1.0 #mu#g/side per day, for 1 d or consecutive 3, 5 and 7 d), a significantly enhanced proliferation occurred on the 1st day and continued until reaching its peak on the 5th day before decreasing on the 7th day. All of the promoting effects of PBG on the ConA-stimulated proliferation of thymocytes were reversed by pretreatment with the 5-HT_(3) receptor antagonist tropisetron (TRP) 5 min prior to the administration of PBG. Interestingly, compared to the treatment with normal saline or TRP + PBG, after a bilateral single-administration of PBG (1.0 #mu#g/side) by i.c.a., the number of c-Fospositive cells in different brain regions significantly increased at 1 h in the CeA, 1-2 h in the hippocampus, 1-2 h in the cortex, 4 h in the hypothalamus and 8 h in the PAG, respectively, with each maximum response at 1 h in the CeA, 2 h in the hippocampus and cortex,and 4 h in the hypothalamus. Subsequently, the number of cells expressing c-Fos gradually reduced to the minimum at 4 h in the CeA,and at 8 h in the hippocampus, cortex and hypothalamus. In conclusion, the 5-HT_(3) receptors in the CeA of rats mediate the modulation of thymus function, at least partly, through the neuroendocrine circuit of the limbic system-cortex-hypothalamus-PAG.

Key words: 5-HT_(3) receptor;1-phenylbiguanide;central amygdala;thymocyte;c-fos;neuroimmunomodulation;Rat

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引用本文：

徐民, 陈伟强, 王基平, Foster D JR, 许德义. 大鼠中央杏仁核5--HT_(3)受体参与胸腺功能调制[J]. 生理学报 2007; 59 (1): 42-50.

Xu Min, Chen Weiqiang, Wang Jiping, Foster D JR, Xu Deyi. 5--HT_(3) receptors in the central amygdala mediate the modulation of thymus function in rats. Acta Physiol Sin 2007; 59 (1): 42-50 (in Chinese with English abstract).