Acinar degranulation in the rat parotid gland induced by neuropeptides

Vasoactive intestinal peptide (VIP, 4 microg kg(-1) min(-1)), substance P (3 microg kg(-1) min(-1)) and neurokinin A (2.5 microg kg(-1) min(-1)) were infused intravenously for 30 min in anaesthetized rats and the effects of these peptides on the parotid gland were examined. VIP reduced the numerical density of parotid acinar secretory granules, storing proteins, by 29 % and the glandular amylase activity by 33 %. Substance P reduced the number of secretory granules by 18 % but the amylase activity was unchanged. These results make VIP and substance P likely contributors to the parasympathetic non-adrenergic, non-cholinergic (NANC)-evoked parotid acinar degranulation. Neurokinin A, on the other hand, caused no reduction in granular number but reduced the glandular amylase activity by 19 %, indicating vesicular protein secretion.