Adenosine modulation of synaptosomal dopamine release.

The effects of adenosine and its analog 2-chloroadenosine on release of preloaded ³H]-dopamine from striatal synaptosomes was explored. Both adenosine and 2-chloroadenosine were found to decrease the amount of dopamine released both by depolarization (with KCl) and by amphetamine. Addition of exogenous adenosine deaminase enhanced dopamine release above controls, and blockade of the endogenous adenosine deaminase activity with deoxycoformycin resulted in a decrease in dopamine release. The methylxanthines, believed to be adenosine antagonists, inhibited dopamine release by an unknown mechanism, and hence it was impossible to evaluate antagonism of the inhibitory effects of adenosine by these agents. The depolarization-induced release of dopamine appeared to be more sensitive to the actions of adenosine than was the amphetamine-induced release. The data obtained so far seem to indicate that adenosine is capable of modulating the release of transmitter substances in brain tissue in a manner analogous to that which has been observed in the peripheral nervous system.