Action of dopamine on the exocrine pancreatic secretion of the intact dog

Abstract

The effects of dopamine and domperidone, a dopamine antagonist, have been studied on the exocrine secretion of the dog pancreas. The purpose of this study was to see if dopamine acted on enzyme secretion and if its action was merely ‘pharmacological’ or had a physiological role. Conscious Beagle dogs, fitted with Thomas cannulae were studied following infusions of dopamine 125–1000 μg kg−1 h−1. During dopamine infusion, a secretory peak lasting 10 min was observed. This was followed by a stable plateau which was approximately 1/3 of the peak. The pattern of water, bicarbonate and protein secretion was similar. The maximum effect was obtained with 500 μg kg−1 h−1 dopamine. The stimulatory action of dopamine was blocked by domperidone, without any detected effect on the central nervous system, but not by propranolol or phenoxybenzamine. Domperidone 10 μg kg−1 almost completely suppressed the secretory response to the maximally effective dose of dopamine. This inhibition was not competitive. Atropine decreased the secretory response to dopamine. The protein response was not observed when dopamine was infused against a background infusion of secretin. This suggests that the effect of dopamine on protein secretion could be due to a wash‐out phenomenon. The maximally effective dose of domperidone, 10 μg kg−1, did not modify the pancreatic response to a solid meal. Thus, in the non‐anaesthetized dog, the effect of dopamine on water and bicarbonate secretion has been confirmed. It is concluded that dopamine had no detectable action on protein secretion and that the physiological role of dopamine with respect to pancreatic secretion is still questionable.

Regulation of Pancreatic Secretion

“…In the dog, the effect of dopamine is blocked by dopamine receptor antagonists but is unaffected by αor β-receptor antagonists. 128,129 In rats and dogs, high doses of dopamine stimulate secretion of pancreatic fluid. 127 These receptors are linked to activation of adenylate cyclase and stimulation of fluid and bicarbonate secretion.…”

Regulation of Pancreatic Secretion

“…There is conflicting evidence regarding the role of dopamine in pancreatic secretion. Dopamine stimulates pancreatic secretion in anesthetized dogs and rats although the effect is negligible in conscious animals (17,55,60,84,131,135). Other data suggest that the secretory response to dopamine differs between dogs, cats, rabbits and rats, and species specific effects must be taken into consideration when evaluating its effects (109).…”