Dopamine actions in vitro on enzyme and electrolyte secretion from normal and sympathectomized rat parotid glands.

Abstract

SUMMARY1. Adult rats were denervated unilaterally by removal of the left superior cervical ganglion or chemically denervated with 6-hydroxydopamine or reserpine. Two weeks later the parotid glands were used for in vitro secretory studies and their catecholamines and major metabolites were measured.2. Noradrenaline concentrations were reduced 2 weeks after surgical sympathectomy and reserpine pre-treatment 18 h previously, whereas 6-hydroxydopamine pre-treatment for 3 days reduced both noradrenaline and dopamine concentrations. 3. Dopamine caused a prominent amylase release from incubated control glands. However, a subsensitivity for dopamine-induced amylase release was recorded on the denervated side.4. Dopamine caused a prominent potassium efflux measured as 86Rb+ efflux from control glands, but was without effect in denervated glands. This is in contrast to noradrenaline-induced 86Rb+ efflux which was equally effective in both denervated and control glands.5. Dopamine caused [3H]noradrenaline efflux in control glands, but was without effect in surgically denervated glands and in glands pre-treated with reserpine or 6-hydroxydopamine.6. It is concluded that dopamine-induced potassium release is caused by a presynaptic action on noradrenergic nerves, whereas dopamine-induced amylase release has a presynaptic and a postsynaptic component. The results suggest a specific action of dopamine in salivary glands, with different effects on enzyme release and ionic fluxes.

Atypical antipsychotics – effects of amisulpride on salivary secretion and on clozapine‐induced sialorrhea

“…The removal of an inhibitory influence of dopamine on the pancreatic secretion was considered as one explanation of the potentiating phenomenon. An explanation of this kind is not valid for salivary secretion, because, in the rat parotid gland, dopamine administration gives rise to a secretory response, an effect attributed to a prejunctional action of the drug, causing the release of acetylcholine and noradrenaline, and/or to a postjunctional action on dopamine D1‐receptors (Sundström et al , 1985; Hata et al , 1986; Michalek and Templeton, 1986; Danielsson et al , 1988). In rats, serotonin administration causes no flow of saliva on its own, but it has been reported to potentiate the acetylcholine‐evoked secretion from the parotid gland (Chernick et al , 1989) and to reduce the acetylcholine‐evoked secretion from the submandibular gland (Turner et al , 1996).…”

Effects of amphetamine on salivary secretion

“…No inhibitory effect by the drug was thus exerted peripherally in the gland. The peripheral effect of amphetamine is most likely to have been exerted via noradrenaline because dopamine has no direct effect on fluid secretion in the rat parotid gland, even though it may induce secretion indirectly by inducing the release of noradrenaline (26, 27). Furthermore, the data seem to contradict the assumption that amphetamine would cause hyposalivation by noradrenergic vasoconstriction.…”

Secretory effects of 5‐hydroxytryptamine following neonatal sympathectomy in rat parotid gland

“…causes no release of noradrenaline, since no influence of 5-HT on "Rb' efflux was discovered in intact control glands. Recently, it was shown that dopamine exerts an indirect effect on potassium efflux by stimulating noradrenaline release from sympathetic nerve endings (Sundstrom et al 1985, Danielsson et al 1988. Noradrenaline then stimulates the a-adrenoceptors on the acinar cells.…”

“…performed with the HPLC technique with electrochemical detection (HPLC-EC) (Danielsson et al 1988). I n brief, frozen salivary gland tissue was weighed, and to each 100 mg of tissue 700 pl of 0.1 M perchloric acid and 70 pl of 10 p~ isoproterenol were added.…”