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mRNA的剪接变体。抗这种变异蛋白（pChAT）的抗血清染色外周胆碱能神经元。在本研究中，我们检测了pChAT在大鼠脑中的免疫组织化学定位。虽然抗血清不能染色脑内已知的胆碱能神经元，但下丘脑后部结节乳头核（TMN）的大细胞神经元被抗血清染色。RT- PCR实验证实pChAT mRNA在大鼠下丘脑后部表达。pchat阳性神经元在细胞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。经秋水仙碱预处理的大鼠双免疫组化染色显示，几乎所有pchat阳性细胞都含有ADA。将霍乱毒素B亚基注入大脑皮层后，细胞核内部分pchat阳性细胞被逆行标记。这些结果表明存在一个假定的从颞下颌神经网络上升的皮质胆碱能通路。

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.