AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 5 601-G606, Copyright © 1987 by American Physiological Society
gamma-Aminobutyric acid stimulates acid secretion from the isolated guinea pig stomach
L. H. Tsai, K. Taniyama and C. Tanaka
Department of Pharmacology, Kobe University School of Medicine, Japan.
gamma-Aminobutyric acid (GABA) content was measured, and the effect of GABA
on acid secretion was studied using the everted preparation of isolated
guinea pig stomachs. GABA contents in the mucosa layer and the remaining
layer were 20-24 nmol/g tissue and 34-42 nmol/g tissue, respectively. GABA
at 10(-6) to 3 X 10(-5) M induced acid secretion, and the maximum secretion
was obtained at 3 X 10(-5) M, that is approximately 1.6-fold of the
spontaneous secretion and approximately half of the amount secreted by
histamine at 3 X 10(-4) M. The GABA-induced acid secretion was inhibited by
bicuculline, scopolamine, pirenzepine, proglumide, and tetrodotoxin, but
not by cimetidine. Muscimol (3 X 10 to 10(-5) M), but not baclofen, induced
acid secretion in a concentration-dependent manner. The responses to GABA
and muscimol were antagonized by bicuculline. Scopolamine and tetrodotoxin
completely inhibited the acid secretion induced by low concentrations of
GABA and muscimol and to some extent the response induced by high
concentrations of muscimol. All these results indicate that GABA induces
acid secretion via the A type of GABA receptor, probably located mainly on
the cholinergic neurons and partially on the nonneuronal cells in the
guinea pig stomach.
