Study on the possibility for drug utilization of peptidergic neurotransmitter using knockout mouse

PACAP与血管活性肠肽（VIP）的氨基酸序列同源性为68%，在中枢和外周神经系统中调节广泛的生理功能。已经克隆了三个编码PACAP/VIP受体亚型的基因，它们以高亲和力结合PACAP，但每个亚型的生理意义尚未完全表征。为了阐明PACAP信号系统的作用，我们在胚胎干细胞中使用基因靶向来破坏PACAP受体基因的外显子2，并表征突变小鼠和野生型小鼠。突变小鼠<125>大脑中的PACAP-27结合和cAMP产生减少。然而，突变小鼠是可存活的和可生育的，并且在形态学、组织学和电生理学上与野生型小鼠没有区别。PACAP受体和PACAP在野生型小鼠和大鼠的交感神经系统中共表达.在交感神经元中，PACAP在转录水平上刺激PACAP受体和PACAP mRNA的表达.在小鼠胰岛素瘤细胞中研究了PACAP产生的机制，结果表明，PACAP作为一种自分泌或旁分泌调节因子参与交感肾上腺系统的持续激活，并通过自分泌机制调节葡萄糖刺激的β细胞胰岛素分泌。然而，完整的PACAP受体并不是小鼠正常发育和生存的先决条件。

PACAP has an amino acid sequence identity of 68% with vasoactive intestinal polypeptide (VIP) and regulates a wide range of physiological functions in the central and peripheral nervous systems. Three genes encoding PACAP/VIP receptor subtypes, which bind PACAP with a high affinity, have been cloned, but the physiological significance of each subtype has not been completely characterized. To elucidate the role of the PACAP signaling system, we have used gene targeting in embryonic stem cells to disrupt exon 2 of the PACAP receptor gene, and characterized the mutant mice as well as wildtype mice.1. The mutant mice had reduced [^<125>I]PACAP-27 binding and cAMP production in their brains.2. The mutant mice, however, were viable and fertile, and morphologically, histologically and electrophysiologically indistinguishable from their wild-type counterparts.3. Coexpression of PACAP receptor and PACAP was seen in the sympathetic nervous system of the wild-type mice and rats.4. In the sympathetic neurons, PACAP stimulates the expression of PACAP receptor and PACAP mRNAs at a transcriptional level.5. The mechanism of the PACAP production was studied in mouse insulinoma cells.In conclusion, these results suggest that PACAP acts as a autocrine or paracrine regulatory factor and contributes to sustained activation of the sympathoadrenal system, and that PACAP regulates glucose-stimulated insulin secretion from beta cells by an autocrine mechanism. However, the intact PACAP receptor is not a prerequisite for normal mouse development of for survival.