PACAP 1-38 as neurotransmitter in the porcine antrum.

The concentration of PACAP 1–38 in porcine antrum amounted to 15.4±7.9 and 20.3±8 pmol/g tissue in the mucosal and muscular layers. PACAP immunoreactive (IR) fibres innervated the muscular (co-localised with VIP) and submucosal/mucosal layers (some co-storing VIP and CGRP) including myenteric and submucosal plexus and blood vessels. Only myenteric nerve cell bodies contained PACAP-IR (co-storing VIP). In isolated perfused antrum, vagus nerve stimulation (8 Hz) and capsaicin (10−5 M) increased PACAP 1–38 release. PACAP 1–38 (10−9 M) increased substance P (SP), gastrin releasing peptide (GRP) and VIP release. PACAP 1–38 (10−8 M) inhibited gastrin secretion and stimulated somatostatin secretion and motility dose-dependently. PACAP-induced motility was strongly inhibited by the antagonist PACAP 6–38 but also by atropine and substance P-antagonists (CP99994/SR48968) but PACAP 6–38 had no effect on vagus-induced secretion or motility. Conclusion: PACAP 1–38 may be involved in antral motility and secretion by interacting with cholinergic, SP-ergic, GRP-ergic and/or VIP-ergic neurones, and may also be involved in afferent reflex pathways.