Release of Previously Incorporated γ-[3H]Aminobutyric Acid in Rabbit Caudate Nucleus Slices |
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Authors: | N Limberger L Späth K Starke |
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Institution: | Pharmakologisches Institut der Universität, Freiburg, F.R.G. |
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Abstract: | 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. |
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Keywords: | Rabbit caudate nucleus γ-Aminobutyric acid release Electrical stimulation Nipecotic acid |
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