CAN THE ACTIONS OF ADRENOCEPTOR AGONISTS AND ANTAGONISTS ON PENTAGASTRIN‐INDUCED GASTRIC SECRETION BE DUE TO THEIR EFFECTS ON HISTAMINE FORMATION?

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Abstract
The effects of some adrenoceptor agonists and antagonists which have been reported to affect histamine formation in leucocytes (Assem & Feigenbaum, 1972) have been investigated on gastric secretion in conscious dogs with Heidenhain pouches. Submaximal secretion in response to pentagastrin was enhanced by propranolol (0.1–1.0 mg/kg i.v.) and phenylephrine (1.0 μg kg−1 min−1 i.v. for 20 min), which increase histamine formation, and was decreased by phentolamine (2 mg/kg i.v.) and isoprenaline (0.05–0.2 μg kg−1 min−1 i.v. for 30 min), which decrease histamine formation. Practolol (2 mg/kg i.v.), which has no effect on histamine formation, had no effect on secretion. Acid secretion in response to histamine was either unaffected or affected in the opposite direction by these drugs. The effects of the drugs on pentagastrin‐induced secretion were not secondary to changes in mucosal blood flow (radioactive aniline clearance). The results are consistent with the hypothesis that acid secretion in response to pentagastrin involves the formation of endogenous histamine.