Effect of adrenergic antagonists on clonidine-induced inhibition of basal gastric secretion in conscious rats.
In unanesthetized rats with chronic gastric fistulas the mechanism of the inhibitory action of clonidine (CLO) on basal gastric secretion was investigated. CLO (0.001-1 mg/kg ip) reduced significantly in a dose-dependent fashion, the basal gastric acid output, and after higher doses no secretion occurred. Noradrenaline (0.1-2.5 mg/kg ip) even in much higher doses was less effective in inhibiting basal gastric secretion in rats. A postsynaptic alpha-adrenergic receptor blocker phenoxybenzamine antagonized only moderately the inhibitory effect of CLO. Phentolamine was more potent in this respect and antagonized significantly, by about a half, the antisecretory effect of CLO. Yohimbine, a presynaptic alpha-adrenoceptor blocker, counteracted insignificantly the inhibitory influence of CLO on basal gastric secretion. The alpha-adrenergic inhibitory receptors in the gastric mucosa, stimulated by CLO, are sensitive to both pre- and post-synaptically acting adrenergic blockers.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005744:Gastric Acid / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects; D010643:Phenoxybenzamine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D010643:Phenoxybenzamine; D015016:Yohimbine; D003000:Clonidine; D009638:Norepinephrine; D010646:Phentolamine