Expression of a splice variant of choline acetyltransferase in magnocellular neurons of the tuberomammillary nucleus of rats

最近在大鼠翼腭神经节中发现了胆碱乙酰转移酶基因的剪接变异体。该变异蛋白的抗血清(PChAT)可使外周胆碱能神经元染色。在本研究中，我们检测了pChAT在大鼠脑内的免疫组织化学定位。虽然该抗血清不能对脑内已知的胆碱能神经元进行染色，但下丘脑后结节乳头核(TMN)的大细胞神经元被该抗血清染色。RT-PCR实验证实大鼠下丘脑后部有pChAT基因的表达。PChAT阳性神经元在核内的分布模式与组氨酸脱羧酶(HDC)和腺苷脱氨酶(ADA)阳性神经元相似。用秋水仙碱处理的大鼠的双重免疫组织化学染色显示，几乎所有的pChAT阳性细胞都含有ADA。大脑皮层注射霍乱毒素B亚单位后，核内部分pChAT阳性细胞被逆行标记。这些结果提示推测存在一条从TMN上行的皮质胆碱能通路。

A splice variant of choline acetyltransferase mRNA has recently been identified in rat pterygopalatine ganglion. An antiserum against this variant protein (pChAT) stained peripheral cholinergic neurons. In the present study, we examined the immunohistochemical localization of pChAT in rat brain. Although the antiserum failed to stain known cholinergic neurons in the brain, magnocellular neurons in the tuberomammillary nucleus (TMN) of the posterior hypothalamus were stained with the antiserum. RT- PCR experiments confirmed the expression of pChAT mRNA in rat posterior hypothalamus. The distribution pattern of pChAT-positive neurons in the nucleus was similar to that positive for histidine decarboxylase (HDC) and adenosine deaminase (ADA). Double immunohistochemical staining in rats pretreated with colchicine indicated mat virtually all pChAT-positive cells contained ADA. Some pChAT-positive cells in the nucleus were retrogradely labeled following the injection of cholera-toxin B subunit into the cerebral cortex. These results suggest the existence of a presumed corticipetal cholinergic pathway ascending from the TMN.