CNS dopamine receptors: effect of prolyl-leucyl-glycinamide and solubilization

In order to elucidate the mechanism of interaction of a peptide L-prolyl leucyl-glycinamide (PLG) with dopamine receptors, we have studied the action of PLG on dopamine receptors in various brain regions. The results support the hypothesis that specific PLG binding sites exist in the central nervous system and these binding sites (receptors) have a modulatory effect on the sensitivity of dopamine receptors. It is also suggested that PLG and its active analogues warrant further vigorous and systematic clinical trials to establish their therapeutic efficacy in Parkinson's disease, neuroleptic drug induced tardive dyskinesia and related extrapyramidal motor disorders. Studies carried out on solubilized dopamine receptors and adenylate cyclase suggest that dopamine receptors sites coupled to neurolic drug action and adenylate cyclase linked receptor sites might be closely interrelated. The preliminary results on lymphocyte dopamine binding sites suggest an increase in binding in schizophrenic patients, however, receptor criteria (stereospecific binding, saturation, etc.) could not be met for these binding sites (see Rotstein et al., 1983, for details).