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

垂体腺苷环化酶激活多肽的超微结构定位用免疫组织化学方法对大鼠下丘脑神经内分泌细胞中的一氧化氮合酶(NOS)和谷氨酸进行了观察，以探讨其功能意义。免疫组织化学染色和组织切片原位杂交发现，PACAP样免疫反应轴突终末与大鼠下丘脑视上核加压素样免疫反应细胞突起和胞体形成突触。原位杂交显示，PACAP 1型受体(PACAP R-1)在大鼠下丘脑视上核加压素样免疫反应神经元中高水平表达PACAP R-1。这些结果提示，PACAP阳性神经元可能通过PACAP 1型受体调节加压素的分泌，PACAP可能通过调节胞浆cAMP水平而在加压素的释放和加压素基因表达的诱导中发挥生理作用。在大鼠下丘脑室旁核，谷氨酸能和GABA能轴突终末与谷氨酸受体亚单位(NMDA-R1)免疫反应阳性终末形成突触接触。这些结果提示，NMDA-R1神经元可能受兴奋性神经元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.