EFFECTS OF CATECHOLAMINES AND THEIR INHIBITORS ON ISOLATED CANINE PANCREAS .2. DOPAMINE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 72  (4) , 719-723
Abstract
Dopaminergic agonists (dopamine, 2, 10, 50 and 250 .mu.g; apomorphine, 1 mg; noradrenaline [norepinephrine], 2, 20 and 200 .mu.g) and inhibitors (haloperidol, 5 mg; pentamethonium, 500 mg; phenoxybenzamine, 15 mg and atropine sulfate, 10 mg), were tested on isolated perfused canine pancreas under basal conditions and under stimulation by a background of secretin (0.1, 0.5 and 10.0 clinical unit/h) or of cerulein (1200 ng/h). Low doses of dopamine induced a vasodilation inhibited by haloperidol. Large doses induced a vasoconstriction, presumably by stimulation of .alpha. adrenergic receptors. Dopamine stimulated hydrelatic secretion. Calculated maximal response was about 1/2 that of secretin. This response was inhibited by haloperidol but not by atropine, pentamethonium and phenoxybenzamine. No acinar degranulation was observed after stimulation by dopamine. The response to secretin was not altered by haloperidol. Blood vessels and pancreatie tissue apparently contain specific receptors to dopamine different from secretin receptors. Secretory response to noradrenaline after phenoxybenzamine was inhibited by haloperidol, suggesting that this effect was mediated by the stimulation of dopamine receptors of the cells. A hypothetical representation of the interrelation between dopamine, secretin and noradrenaline is discussed.

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