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，我们研究了pChAT在大鼠脑内的免疫组织化学定位。虽然抗血清未能染色已知的胆碱能神经元在大脑中，大细胞神经元在结节乳头核（TMN）的后下丘脑染色的抗血清。RT-PCR实验证实pChAT mRNA在大鼠下丘脑后部有表达. 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）阳性神经元的分布模式相似。在用秋水仙碱预处理的大鼠中，双重免疫组织化学染色表明几乎所有pChAT阳性细胞都含有ADA。将霍乱毒素B亚单位注入大脑皮质后，可逆行标记细胞核内的pChAT阳性细胞。这些结果表明，存在一个假定的皮质胆碱能通路上升的TMN。

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.