Modulation of CNS dopamine receptors by peptides.

L-prolyl-L-leucyl-glycinamide (PLG), when administered concurrently with neuroleptic drug, blocked the development of dopamine receptor supersensitivity both at the behavioral and biochemical level. Chronic administration of haloperidol resulted in development of cholecystokinin (CCK) receptor supersensitivity in the mesolimbic regions of the brain. There was no change in equilibrium dissociation constant (KD) for CCK binding. The results are discussed in relation to modulation of dopamine receptor by peptides and possible models of interaction of peptides with dopamine receptors are proposed.