Physiological analysis of the role of PACAP using transgenic and knockout mice

本研究利用本实验室新近培养的PACAP基因敲除小鼠（PACAP^<-/->）、胰腺过表达PACAP的转基因小鼠（PACAP- tg）和PACAP （PAC_1）受体外显子2靶向小鼠（PAC_1^<-/->），探讨了内源性PACAP在中枢和周围神经系统中的生理和病理生理作用。通过这些体内诱变研究，我们得到了以下结果：1。(1) PACAP^<-/->小鼠在开阔场地表现出多动和爆发性跳跃行为，探索行为增加，焦虑减少。这些异常行为可通过抗精神病药物和SSRI得到改善。(2) PACAP^<-/->小鼠脉冲前对声惊反应的抑制明显受损。这些结果提供了证据，表明PACAP在精神运动行为的调节中起着以前未被描述的作用，并表明PACAP^<-/->小鼠的表型在一定程度上与人类的相似。pacap ^<-/->小鼠和PAC_1^<-/->小鼠海马长期增强（LTP）功能受损。此外，行为学研究发现海马依赖的联想学习存在缺陷，暗示pacap能神经元参与了脑高级功能的调节。在PACAP^<-/->小鼠中，神经性疼痛和炎症性疼痛模型中的疼痛传递异常性痛和痛觉过敏明显减少。在PACAP^<-/->小鼠中，光诱导的相位重置和视交叉上核（SCN）中c-Fos的表达减弱，突出了PACAP在昼夜光干扰中的体内作用。(1) PACAP转基因可改善链脲佐菌素诱导的PACAP- tg小鼠糖尿病。值得注意的是，在链脲霉素处理的PACAP-Tg小鼠中，观察到5-溴-2-脱氧尿苷（BrdU）阳性的β细胞增加。(2)将PACAP-Tg与致死性黄鼠KKA^y（肥胖-糖尿病遗传模型）杂交。KKA^y小鼠表现出与代偿性高胰岛素血症和胰岛增生相关的显著高血糖；然而，在携带PACAP转基因的KKA^y小鼠中，高胰岛素血症和胰岛增生均被显著抑制。目前的数据表明，PACAP对I型糖尿病和肥胖相关（II型）糖尿病具有保护作用，并且PACAP可能参与β细胞新生。这是首次报道PACAP在胰岛增生和β细胞新生中的体内作用，提供了与PACAP信号通路相关的药物可能具有治疗糖尿病的治疗价值。少

This study examined the physiological and pathophysiological roles of endogenous PACAP in the central and peripheral nervous system using PACAP gene knockout (PACAP^<-/->) mice, transgenic mice overexpressing PACAP in the pancreas (PACAP-Tg), and PACAP (PAC_1) receptor exon 2-targeted (PAC_1^<-/->) mice which were recently generated in this laboratory. Through these in vivo mutagenesis studies, we obtained the following results.1. Psychomotor function(1) PACAP^<-/-> mice exhibited hyperactive and explosive jumping behaviors in an open field, and increased exploratory behavior and less anxiety. These aberrant behaviors are ameliorated by the antipsychotic drug and SSRI.(2) PACAP^<-/-> mice exhibited a significant impairment of prepulse inhibition of the acoustic startle response.These results provide evidence that PACAP plays a previously uncharacterized role in the regulation of psychomotor behaviors and suggest that the phenotype of PACAP^<-/-> mice in part resembles those in human sc … More hizophrenia and/or attention deficit/hyperactivity disorder (ADHD).2. Hippocampal functionPACAP^<-/-> mice and PAC_1^<-/-> mice showed an impairment of hippocampal long-term potentiation (LTP). In addition, the behavioral study revealed a deficit in hippocampus-dependent associative learning, implicating PACAP-ergic neurons in regulation of higher brain functions.3. Pain transmissionAllodynia and hyperalgesia in the neuropathic and inflammatory pain models were significantly reduced in PACAP^<-/-> mice.4. Circadian rhythmThe light-induced phase resetting and c-Fos expression in the suprachiasmatic nucleus (SCN) were attenuated in PACAP^<-/-> mice, highlighting the in vivo role of PACAP in circadian photoentrainment.5. Glucose and insulin homeostasis(1) The PACAP transgene ameliorated streptozotocin-induced diabetes in PACAP-Tg mice. Notably, an increase in 5-bromo-2-deoxyuridine (BrdU)-positive β cells in the streptozotocin-treated PACAP-Tg mice was observed.(2) We crossed PACAP-Tg and lethal yellow KKA^y mice, a genetic model for obesity-diabetes. KKA^y mice showed marked hyperglycemia associated with compensatory hyperinsulinaemia and islet hyperplasia; however, both hyperinsulinemia and islet hyperplasia were significantly suppressed in KKA^y mice carrying the PACAP transgene.The present data suggest a protective role for PACAP against type I diabetes as well as obesity-associated (type II) diabetes, and the possible involvement of PACAP in the β cell neogenesis. This is the first report suggesting in vivo roles of PACAP on islet hyperplasia and β cell neogenesis, providing the possibility that drugs associated with PACAP-signaling pathways might be of therapeutic value for the treatment of diabetes. Less