PITUITARY ADENYLATE-CYCLASE ACTIVATING PEPTIDE (PACAP) IN SALIVARY-GLANDS OF THE RAT - ORIGIN, AND SECRETORY AND VASCULAR EFFECTS

Pituitary adenylate cyclase activating peptide (PACAP)-38. injected i. v. to the anaesthetized rat, evoked secretion of saliva from the three major salivary glands. the submandibular glands responding with the g reatest and the sublingual glands with the smallest volumes. The parot id saliva was rich in amylase and protein. in vitro. pieces of parotid and submandibular gland tissues released K+ and protein in response t o PACAP-38, with atropine and adrenoceptor antagonists present. The bl ood flow in the submandibular gland increased in response to PACAP-38, despite a marked fall in mean aortic blood pressure. PACAP is a vasoa ctive intestinal peptide (VIP)-like neuropeptide. A comparison between the two peptides showed PACAP-38 to be more effective than VIP with r espect to vascular responses and less or equi-effective with VIP with respect to the secretory responses, thus suggesting the involvement of PACAP type I and type ii receptors. respectively PACAP-38 and -27 wer e present in the parotid gland as judged by radioimmunoassay, the conc entration of the former being about twice that of the latter. Parasymp athetic denervation, by cutting the auriculo-temporal nerve, reduced t he total parotid gland contents of PACAP-38 and -27 by 23 and 44%. res pectively (compared with a previously demonstrated 95% reduction of VI P). Sympathetic denervation, section of the facial nerve or treatment with the sensory neurotoxin capsaicin did not affect the content of PA CAP. The difference in efficacy between PACAP and VIP in the vascular and secretory responses as well as the difference in localization sugg est that the two peptides play different physiological roles in the sa livary glands.