[Release of gamma-aminobutyric acid from cat colon].
The release of gamma-aminobutyric acid was confirmed in isolated cat colon loaded with tritiated gamma-aminobutyric acid. Thirty to 180 minutes after loading the spontaneous efflux of tritium appeared to fit a single exponential curve with an efflux rate coefficient of 0.002 per minute. Electrical stimulation produced frequency-dependent increases in the tritium efflux and in the contractions. Even 120 minutes later over 91 percent of the total radioactivity in the superfusates was attributable to tritiated gamma-aminobutyric acid. The acid release and the contractions induced by electrical transmural stimulation were inhibited by tetrodotoxin and by a calcium-free medium. Release of the acid was not significant during contractions elicited by nicotine and acetylcholine. These findings indicate that gamma-aminobutyric acid is released from the terminals of neurons in the myenteric plexus of the colon.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002413:Cations, Divalent / Q000494:pharmacology; D002415:Cats; D003106:Colon / Q000294:innervation / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth; D009538:Nicotine / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002413:Cations, Divalent; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D009538:Nicotine; D000109:Acetylcholine; D002118:Calcium