Depletion of acinar secretory granules in the ferret parotid gland: effects of substance P and vasoactive intestinal peptide.

The 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 microgram kg-1 min-1 of each for 40 min) in the pentobarbitone-anaesthetized 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-Arg1, 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.