Vasoactive intestinal peptide (VIP, 4 pg kg-' min-'), substance P (3 pg kg-' min-') and neurokinin A (2.5 pg kg-' min-') 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 ' ' A and the glandular amylase activity by 33 %. Substance P reduced the number of secretory granules by 18 o/u 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. Experimental Physiology (2001) 86.6, 733-738.The parotid gland of the rat has served as model organ for studies on parasympathetic non-adrenergic, non-cholinergk (NANC) secretory mechanisms (Ekstrom, 1999). The gland looses its content of acinar secretory granules, storing secretory proteins, upon electrical stimulation of the parasympathetic innervation in the anaesthetized rat in the presence of atropine and a-and /I-adrenoceptor antagonists (Ekstrom et al. 1988(Ekstrom et al. , 1996. There is also a parasympathetic nerve-evoked acinar degranulation, in the presence of the autonomic receptor blockers, in the conscious animal in response to mastication during feeding (Ekstrom et al. 1993) and to ascorbic acid applied on the tongue (Ekstrom, 2001). Parasympathetic nerve activity, electrically or reflexly elicited, releases the neuropeptides substance P and vasoactive intestinal peptide (VIP) from the parasympathetic nerve fibres of the gland (Ekstrom et al. 1985; AsztCly et al. 1996). Upon intravenous administration substance P causes the gland to secrete a copious flow of saliva poor in protein, while VIP evokes a small, viscous and very protein-rich flow of saliva (Ekstrom et al. 1983). Neurokinin A, like substance P a member of the tachykinin family, also causes secretion of parotid saliva but is less potent than substance P. Furthermore, the amylase concentration is higher in the neurokinin A-induced saliva than in the substance P-induced saliva, suggesting that the two tachykinins may act on different populations of tachykinin receptors in the gland. These tackykinins and VIP are confined to periacinar parasympathetic nerve fibres (Ekstrom, 1999).Substance P, neurokinin A and VIP are possible transmitters involved in the parasympathetic non-adrenergic, noncholinergic-induced exocytotic response of the parotid gland. Therefore, it was investigated whether administration of these three neuropeptides causes granular depletion of the parotid acinar cells. Observations were also made on the effect on salivary secretion and amylase output as well as on amylase gland content. The drugs were infused intravenously for 30 min in the anaesthetized rat. METHODSA total of 53 adult female Sprague-Dawley rats (B &...

SUMMARYThe acinar cells of the ferret parotid gland are supplied with parasympathetic nerve fibres containing vasoactive intestinal peptide (VIP) and substance P. In this study intracarotid infusions of the two peptides (0-5-1-0 #g kg-min-1 of each for 40 min) in the pentobarbitoneanaesthetized ferret, treated with atropine and adrenoceptor antagonists, induced a loss of acinar secretory granules from this gland, by 32% in response to VIP and by 46% in response to substance P. Stimulation of the parasympathetic auriculo-temporal nerve (40 Hz, in the presence of adrenoceptor antagonists) caused a larger loss of acinar granules from the gland than stimulation of the sympathetic superior cervical ganglion (intermittently, 50 Hz for 1 s every 10th second, in the presence of atropine) over 40 min (52 % versus 10 %). A 27 % granular loss in response to parasympathetic stimulation followed upon atropinization. The parasympathetic response was not further diminished by the tachykinin antagonist Spantide ((D-Arg',D-Pro2, D-Trp7 9,Leu)-substance P). Thus, despite the large exocytotic response to the infusion of substance P, the parasympathetic non-adrenergic, non-cholinergic secretion of storage granules seemed, under the present experimental conditions, to occur independently of the action of substance P.