Apostolakis Ede Marie, Riherd Deanna N, O'Malley Bert W
Department of Molecular and Cell Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
Mol Endocrinol. 2005 Nov;19(11):2798-811. doi: 10.1210/me.2004-0387. Epub 2005 Jun 23.
Pituitary adenylate cyclase-activating polypeptide (PACAP) acts as a feed-forward, paracrine/autocrine factor in the hypothalamic ventromedial nucleus (VMN) for receptivity and sensitizes pituitary hormone release for ovulation. The present study examined receptor(s) and signaling pathway by which PACAP enhances rodent lordosis. PACAP binds to PACAP (PAC1)- and vasoactive intestinal peptide-preferring receptors (VPAC1, VPAC2). Ovariectomized rodents primed with estradiol (EB) were given PACAP or vasoactive intestinal peptide directly onto VMN cells. Only PACAP facilitated receptivity. Pretreatment with VPAC1 and VPAC2 inhibitors blocked both PACAP- and progesterone (P)-induced receptivity. Antisense (AS) oligonucleotides to PAC1 (not VPAC1 or VPAC2) inhibited the behavioral effect of PACAP and P. By real-time RT-PCR, EB, P and EB+P enhanced VMN mRNA expression of PAC1. Within the total PAC1 population, EB and EB+P induced expression of short form PAC1 and PAC1hop2 splice variants. Finally, blocking cAMP/protein kinase A signaling cascade by antagonists to cAMP activity and protein kinase A or by antisense to dopamine- and cAMP-regulated phosphoprotein of 32 kDa blocked the PACAP effect on behavior. Collectively, these findings provide evidence that progesterone receptor-dependent receptivity is, in part, dependent on PAC1 receptors for intracellular VMN signaling and delineate a novel, steroid-dependent mechanism for a feed-forward reinforcement of steroid receptor-dependent reproductive receptivity.
垂体腺苷酸环化酶激活多肽（PACAP）作为一种前馈性的旁分泌/自分泌因子，在下丘脑腹内侧核（VMN）中发挥作用，调节接受性，并使垂体激素释放对排卵敏感。本研究探讨了PACAP增强啮齿动物脊柱前凸的受体及信号通路。PACAP可与PACAP（PAC1）受体和血管活性肠肽优先受体（VPAC1、VPAC2）结合。给用雌二醇（EB）预处理的去卵巢啮齿动物的VMN细胞直接注射PACAP或血管活性肠肽。只有PACAP能促进接受性。用VPAC1和VPAC2抑制剂预处理可阻断PACAP和孕酮（P）诱导的接受性。针对PAC1（而非VPAC1或VPAC2）的反义（AS）寡核苷酸可抑制PACAP和P的行为效应。通过实时逆转录聚合酶链反应，EB、P以及EB + P可增强VMN中PAC1的mRNA表达。在总的PAC1群体中，EB和EB + P可诱导短型PAC1和PAC1hop2剪接变体的表达。最后，通过cAMP活性拮抗剂、蛋白激酶A拮抗剂或针对32 kDa多巴胺和cAMP调节磷蛋白的反义寡核苷酸阻断cAMP/蛋白激酶A信号级联反应，可阻断PACAP对行为的影响。总的来说，这些发现提供了证据，表明孕酮受体依赖性接受性部分依赖于PAC1受体参与VMN细胞内信号传导，并阐明了一种新的、类固醇依赖性机制，用于前馈增强类固醇受体依赖性生殖接受性。
