Abstract
1. The characteristics of the release of adenosine have been examined from slices of rat cerebral cortex after incubation with [3H]adenine or [3H]adenosine. 2. Increasing the potassium concentration of the extracellular medium to 36 or 54 mM did not evoke any release, but release was observed in the first post-potassium sample. This occurred whether potassium was present for 2 or 10 min. 3. Calcium-free solutions or verapamil prevented the post-potassium release of tritium. Tetraethylammonium bromide and 4-aminopyridine had no effect. 4. Ouabain (100 microM) induced the release of tritium, and did not prevent an additional increment of release after potassium stimulation. Ouabain induced release did not occur in calcium-free or sodium-free media, but was increased in low calcium (0.1 mM) medium. 5. It is concluded that the characteristics of adenosine release are unlike those of conventional neurotransmitters. It is suggested that the release is associated with the influx of sodium and calcium ions through sodium channels.