Release of previously incorporated gamma-[3H]aminobutyric acid in rabbit caudate nucleus slices.
The release of gamma-aminobutyric acid (GABA) was studied in slices of the head of the rabbit caudate nucleus. The slices were preincubated with [3H]GABA and then superfused. Aminooxyacetic acid was present throughout. Both the tritium in the slices and that in the superfusate consisted practically entirely of [3H]GABA. Stimulation for 2 min by electrical field pulses of 3 ms width and 9 V/cm voltage drop (36 mA current strength) at 5 or 20 Hz elicited an overflow of [3H]GABA that amounted to 0.23 or 0.47% of the tritium content of the tissue, respectively, and was diminished by 85% in the presence of tetrodotoxin. At higher current strength, less of the stimulation-evoked overflow was tetrodotoxin-sensitive. cis-1,3-Aminocyclohexane carboxylic acid diminished the uptake of [3H]GABA into the tissue but did not change the percentage released by electrical stimulation. Ca2+ withdrawal greatly accelerated basal [3H]GABA efflux and almost abolished the response to stimulation. Nipecotic acid 10-1,000 microM enhanced both the basal and (up to eightfold) the stimulation-evoked overflow. The method described allows us to elicit electrically a quasiphysiological, i.e., Ca2+-dependent and tetrodotoxin-sensitive, neuronal release of [3H]GABA. Nipecotic acid diverts released [3H]GABA from reuptake to overflow.
D000596:Amino Acids / Q000494:pharmacology; D000598:Amino Acids, Cyclic; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D008297:Male; D009557:Nipecotic Acids / Q000494:pharmacology; D011392:Proline / Q000031:analogs & derivatives*; D011817:Rabbits; D013779:Tetrodotoxin / Q000494:pharmacology; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D003509:Cyclohexanecarboxylic Acids; D009557:Nipecotic Acids; D014316:Tritium; C030278:nipecotic acid; C015666:3-aminocyclohexanecarboxylic acid; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D011392:Proline; C010983:homoproline; D002118:Calcium