ADENOSINE INHIBITION OF γ‐AMINOBUTYRIC ACID RELEASE FROM SLICES OF RAT CEREBRAL CORTEX

Abstract

1 The effect of purine compounds on the potassium-evoked release of ¹⁴C-labelled γ-aminobutyric acid (GABA) has been studied in 400 μm slices of rat cerebral cortex in vitro. 2 Adenosine and adenosine 5′ monophosphate (AMP) inhibited the release of GABA at 10⁻⁵ to 10⁻³ m. Adenosine triphosphate (ATP) produced a significant inhibition of release only at 10⁻³ m. 3 Theophylline 10⁻⁴ or 10⁻³ m reduced the inhibitory effect of adenosine, but did not change basal release of GABA. 4 Dipyridamole 10⁻⁵ m itself reduced evoked GABA release, but did not prevent the inhibitory effect of adenosine, implying that adenosine was acting at an extracellularly directed receptor. 5 Calcium removal or antagonism by verapamil reduced the evoked release of GABA, but adenosine did not produce any further reduction of the calcium-independent release. This may indicate that the inhibitory effect of adenosine on GABA release results from interference with calcium influx or availability within the terminals.