Immunoreactive and biologically active somatostatin-like material in the human retina

[³HSpiroperidol and [³H](?)-sulpiride specific binding have been used to assay for D₁ and D₂ dopaminergic recognition sites in striatal membranes of aged rats. While [³H]spiroperidol binding shows a decreased number of binding sites, no changes have been detected in [³H](?)-sulpiride binding, which is a marker for D₂ dopaminergic receptors. Data obtained with GTP and DA-dependent adenylyl cyclase activity confirm the hypothesis that aging selectively affects in rats those dopaminergic receptors coupled to the formation of cyclic AMP (D₁).