Figure 1

Elution profile of KCl-stimulated [³H]GABA release from inferior colliculus slices. Inferior colliculus slices were incubated with 11 nM [³H]GABA for 30 min and perfused (0.5 ml/min) with Krebs buffer for 30 min in a Brandel superfiltration apparatus. Fractions (1 ml) were then collected every 2 min. Krebs buffer containing 25 mM KCl was loaded into the system at times corresponding to fraction 4 and 12 (short black lines) which elicited [³H]GABA release peaks in fractions 6–7 and fraction 14–15. Krebs buffer containing modulating drugs (1 μM morphine-long blue line) was added from the time corresponding to fraction 8. Scintillation fluid (3 ml) was added to the each fractionated eluate and to the solubilized tissue samples and counted. Data are expressed as fractional release which is calculated as the radioactivity released in one fraction divided by the amount of radioactivity present in the tissue just before that fraction. The two peaks from each elution profile are referred to as S1 and S2. The data from a representative experiment are shown.