ELECTRICALLY INDUCED RELEASE OF [³H]GABA FROM NEOCORTICAL THIN SLICES. EFFECTS OF STIMULUS WAVEFORM AND OF AMINO‐OXYACETIC ACID

Abstract

Abstract— The efflux of [ 3 H]GABA or [ 14 C]GABA from superfused neocortical thin slices, held on quick transfer electrodes, has been compared with that of the non‐transmitter amino acid model [ 14 C]α‐ amino‐isobutyrate (AIB), and, to a lesser extent, with [ 3 H]norepinephrine. Electrical stimulation of the slices with sine‐wave current (50 Hz); rectangular, biphasic pulses, (80/s, 3 ms); or rectangular, monophasic pulses (100/s, 5 ms), was unable to release GABA at stimulating potentials that are able to release known transmitter substances. Release of GABA and AIB was only seen with higher applied potentials, when also non‐transmitter amino acids were released. It was also found that amino‐oxyacetic acid(10 ‐5 M and 5 × 10 ‐5 M) increased the excitability of the slices, and allowed the release of both GABA and AIB to occur with weaker stimuli. This effect was independent of extracellular calcium.