Adenosine modulation of dynorphin B release by hippocampal synaptosomes

A rat hippocampal preparation enriched in mossy fiber synaptosomes was employed in an attempt to expose any relationship between endogenous adenosine and the release of dynorphin B-like immunoreactivity (DynB-LI). Presumptive blockade of purinergic receptors increased the spontaneous release of DynB-LI, and reducing synaptic adenosine by exogenous adenosine deaminase increased the K(+)-evoked release. Evoked release of DynB-LI was reduced by inhibitors of adenosine uptake and 5'-nucleotidase. Taken together, these data suggest that adenosine endogenous to hippocampal mossy fiber synaptosomes serves to inhibit the release of one of the peptide neuromodulators of this preparation, and provide support for the concept of autoregulation of release.