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

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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.