Depletion of vasoactive intestinal peptide and substance P in parotid glands of atropinized rats during reflex secretion

Abstract

SUMMARYRats previously starved for 30 h were offered hard chow over a period of 80 min, and the effect of eating on the parotid gland content of vasoactive intestinal peptide (VIP), substance P and neuropeptide Y (NPY) was examined. In rats pretreated with I.P. atropine and o-and ,b-adrenoceptor blocking agents, the total amounts of VIP and substance P were reduced after feeding by 23 and 42 %, respectively; in contrast the NPY content was not significantly affected. Similarly, in animals given atropine alone the VIP content was reduced by 25 % and substance P by 40 % after feeding. In the absence of autonomic receptor blockade, there was no loss of parotid neuropeptide content in response to feeding. Neither an intact sympathetic innervation nor a capsaicin-sensitive sensory innervation was a prerequisite for depletion of parotid neuropeptides in the presence of atropine and adrenoceptor blockers. The observed decrease in neuropeptide content is thought to reflect an imbalance between peptide release from nerve terminals and their replenishment by axonal transport, this imbalance resulting from the unusually high demands on the parasympathetic non-adrenergic, non-cholinergic (NANC) mechanism. Under normal conditions salivary peptidergic mechanisms are spared as seen in the absence of autonomic receptor blockade.

Effect of the neuropeptides vasoactive intestinal peptide, peptide histidine methionine and substance P on human major salivary gland secretion

“…So far, the rat and the mink are the only species where VIP per se , in addition, has been found to evoke an overt flow of saliva (Ekström et al , ; Tobin and Ekström, ). In rats, VIP is released from the parasympathetic nerve endings upon reflex stimulation of the salivary glands (Asztély et al , ). In humans, VIP and PHM, released upon parasympathetic activity, are likely to interact positively not only with acetylcholine but also with noradrenaline, released upon sympathetic activity, with respect to both fluid and protein secretion in analogy with the previous animal studies (Ekström, ).…”

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

“…Therefore, the present results do not exclude a role for substance P in acinar degranulation at lower frequencies of parasympathetic activation than were used in our experiments or in situations of reflexly elicited parasympathetic secretion of saliva. A marked degranulation occurs in the parotid gland of the conscious rat in response to chewing, which is associated with the release of substance P and VIP (Asztely, Ekman, Tobin & Ekstrom, 1996). This work was supported by grants from the Swedish Medical Research Council (05927).…”