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

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.