Adenosine inhibits glutamate stimulated [3H]d-aspartate release from cerebellar granule cells

The release of ³H]d-aspartate from cultured cerebellar granule cells (a glutamatergic neuron) was studied. It was found that the l-glutamate induced stimulation of ³H]d-aspartate release from the neurons could be decreased 30–40% by adenosine, cyclohexyladenosine and (−)N⁶-(2-phenylisopropyl)-adenosine all in the dose range 1–10 μM. The effects of adenosine agonists could be blocked and even reversed by the adenosine antagonist theophyllin indicating a possible endogenous adenosine tonus on the neurons. The results add further evidence to the notion that adenosine A₁ receptors present on parallel fiber terminals in the cerebellar cortex are involved in the regulation of glutamate transmitter release from the nerve terminals.