Binding affinity of N3-substituted uridine for synaptic membrane and their CNS depressant effects

The binding affinity for synaptic membrane from bovine thalamus of N3-phenacyl substituted pyrimidine nucleosides having CNS depressant activity was examined by radio receptor assay. N3-Phenacyl derivatives of uridine, thymidine, deoxyuridine, 6-azauridine and arabinofuranosyluracil inhibited specific [3H]uridine binding and exhibited hypnotic activity. However, N3-phenacyl-2',3'-O-isopropylideneuridine, of which structure was different from sugar moiety of N3-phenacyluridine, showed neither the binding affinity nor the hypnotic activity. The results indicated that CNS depressant effect of pyrimidine nucleoside derivatives might relate to uridine binding affinity, so called uridine receptor.