Turnover of specific [3H]spiperone and [3H]N, n-propylnorapomorphine binding sites in rat striatum following phenoxybenzamine administration

Inclusion of phenoxybenzamine into incubates containing rat striatal preparations equipotently displaced specific striatal [ 3 H]spiperone and [ 3 H]NPA binding. Pre-incubation of striatal membranes with phenoxybenzamine followed by extensive washing equipotently inhibited the subsequent specific [ 3 H]spiperone or [ 3 H]NPA binding. In both displacement and pre-incubation experiments phenoxybenzamine caused complete inhibition of specific [ 3 H]spiperone binding to rat striatal membranes, but only partially inhibited specific [ 3 H]NPA binding. Following parenteral administration to rats, phenoxybenzamine caused a marked inhibition of ex vivo specific [ 3 H]spiperone binding in striatal tissue preparations from these animals which lasted approximately 24 hr following in vivo drug administration. In contrast, administration of phenoxybenzamine caused only a transient change in ex vivo specific [ 3 H]NPA binding. Phenoxybenzamine causes irreversible inhibition of [ 3 H]spiperone and [ 3 H]NPA binding in vitro . In vivo administration of phenoxybenzamine discriminates between [ 3 H]spiperone and [ 3 H]NPA in ex vivo studies suggesting that these binding sites have different turnover rates.