AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 5 717-G721, Copyright © 1983 by American Physiological Society
Release of endogenous and labeled GABA from isolated guinea pig ileum
K. Taniyama, Y. Miki, M. Kusunoki, N. Saito and C. Tanaka
The release of gamma-aminobutyric acid (GABA) was studied by comparing the
properties of labeled GABA released from preloaded preparations to those of
endogenous GABA released from the isolated guinea pig ileum. The
spontaneous release of endogenous GABA was 4.46 +/- 0.10 pmol X min-1 X g
wet wt-1, and the fractional rate of endogenous GABA release was much
lower. The ratio of evoked to spontaneous release of endogenous GABA was
high compared with that of labeled GABA. The electrical transmural
stimulation-evoked release of labeled and endogenous GABA was inhibited by
superfusion with tetrodotoxin and Ca2+-free Krebs-Ringer solution
containing 1 mM ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic
acid. Thus the nature of the stimulation-evoked release of labeled GABA was
similar to that of endogenous GABA. These results indicate that the
released GABA is neuronal in origin and provide additional evidence for the
presence of GABA-ergic neurons in the guinea pig ileum.
