Abstract
Effects of atropine (ATR, 0.5 mg/kg, i.v.), proglumide (PGM, 100 mg/kg, i.v.)and metiamide (MTM, 0.4 mg/kg, i.v.) on gastric acid secretion induced by vagal stimulation, carbamylcholine (CCh, 5μg/kg, i.v.), tetragastrin (TG, 5μg/kg, i.v.) and histamine (Hist, 10μg/kg, i.v.) injections were examined by means of continuous pH recording of proventricular effluent in urethan anesthetized chickens. Birds were operated for fitting an esophageal cannula and gastric fistel, artificial respiration, bilateral vagotomy and instillation of physiological saline solution. Electrical stimulation (0.1msec duration, 30volts, 50 Hz, for 40 to 60 sec) was applied to Trunks communis n. vagi at the proximal region of the proventriculus where the proventricular rami (Rr. gastrici glandulares) branched. The vagal stimulation and the administration of CCh produced a biphasic profile of pH fall response consisting of an early transient and a secondary lasting phases. The transient response was larger in the degree of pH fall than the lasting one, and was inhibited by ATR but not by PGM and MTM. The lasting response was reduced by all of the three inhibitors. PGM and MTM inhibited pH fall responses induced by TG and Hist, respectively. These results show that the vagally stimulated acid secretion consists of an early transient response which is major component and a secondary lasting response Which is minor component. It is suggested that the transient response is directly mediated by cholinergic transmission and the lasting response is possibly mediated by endogenous gastrin and histamine in the pathways sensitive to PGM and MTM.
