Dopamine-induced amylase secretion from guinea-pig submandibular gland

1. The effects of dopamine, 5-hydroxydopamine (5-OHDA) and noradrenaline on amylase secretion from the guinea-pig submandibular gland were investigated under in vitro conditions. 2. All three amines greatly enhanced amylase secretion. Blockade of dopamine beta-hydroxylase did not inhibit the response to dopamine. 3. Noradrenaline and dopamine stimulated amylase release from salivary glands of reserpine-treated animals, whereas 5-OHDA had no stimulatory effect on secretion in guinea-pigs pretreated with reserpine. 4. Haloperidol completely inhibited dopamine-induced enzyme discharge, but did not affect noradrenaline-initiated secretion. 5. Apomorphine caused a slight enzyme release by itself; it diminished the dopamine secretory effect, but did not modify that of noradrenaline. 6. Pimozide and fluspirilene attenuated the dopamine-induced enzyme discharge, but compared with haloperidol they were less effective. 7. It is concluded that dopamine exerts a secretagogic action different from that of noradrenaline. The possible presence of a specific dopamine receptor in salivary glands is discussed.