Physiological significance of enzyme-activating substances in the neuroendocrine cells.

垂体腺苷酸环化酶激活肽的超微结构定位，用免疫组织化学方法观察了大鼠下丘脑神经内分泌细胞内一氧化氮合酶（NOS）和谷氨酸（Glu）的表达，并观察到PACAP样免疫反应阳性轴突终末与加压素形成突触。用包埋前免疫双标法观察了大鼠下丘脑视上核内PACAP 1型受体的阳性细胞突起和胞体，原位杂交显示PACAP 1型受体在视上核内有高水平表达用免疫组织化学染色和原位杂交相结合的方法，发现大鼠下丘脑视上核内的加压素样免疫反应神经元强烈表达PACAP R-1 mRNA。这些结果表明，PACAP神经元可能通过PACAP 1型受体调节加压素的分泌，PACAP可能在加压素的释放中起生理作用，并通过调节胞浆cAMP水平诱导加压素基因的表达。NOS样免疫反应神经元的细胞构筑与多巴胺能神经元相似。NOS样免疫反应轴突终末与一些未知神经元形成突触，在大鼠下丘脑室周围核中，谷氨酸能和GABA能轴突终末与谷氨酸受体亚单位（NMDA-R1）免疫反应轴突形成突触接触。这些结果表明，含NMDA-R1的神经元可以受到兴奋性和抑制性神经元的调节。

Ultrastructural localization of pituitary adenylate cyclase activating polypeptide (PACAP), nitric oxide synthase (NOS) and glutamate in the neuroendocrine cells of the rat hypothalamus were observed to examine their functional significances by electron microscopic immunohistochemistry.PACAP-like immunoreactive axon terminals were found to make synapses with the vasopressin-like immunoreactive cell processes and cell bodies in the supraoptic nucleus of the rat hypothalamus using preembedding double immunostaining.In situ hybidization revealed high-level expression of PACAP type 1 receptor (PACAP R-1) mRNA in the vasopressin-like immunoreactive neurons in the supraoptic nucleus of the rat hypothalamus.We found the vasopressin-containing neurons in the supraoptic nucleus strongly expressed PACAP R-1 mRNA by combining immunohistichemical staining and in situ hybridization of the same tissue sections. These findings suggest that PACAP-containing neurons might regulate the secretion of vasopressin via PACAP type 1 receptor.PACAP may have a physiological role in the release of vasopressin, as well as in induction of the expression of the gene for vasopressin via regulation of the cytosolic level of cAMP.Concerning NOS-containing neurons in the dorsal raphe nucleus, the cytoarchitecture of the NOS-like immunoreactive neurons was similar to that of the serotonergic neurons. NOS-like immunoreactive axon terminals were found to make synapses with some unknown neurons.In the rat hypothalmic periventricular nucleus, glutamatergic and GABAergic axon terminals formed synaptic contacts on the glutamate receptor subunit (NMDA-R1) immunoreactive endrites. These results suggest that NMDA-R1 containing neurons could be regulated by excitatory and inhibitory neurons.