Effect of neuropeptide-EI on the binding of [3H]SCH 23390 to the dopamine D1 receptor in rat striatal membranes

We have previously demonstrated that neuropeptide-EI, at high doses, stimulates the production of cAMP, in caudate putamen, through the activation of adenylate cyclase coupled to specific D₁ receptors. The aim of the present work was to find evidences for a probable interaction between this neuropeptide and the dopamine D₁ receptor in the mammalian central nervous system. The present data show that neuropeptide-EI, at high concentrations, affected both the maximum binding and the apparent affinity of [n-methyl-³H] (R)-(+)-8 chloro-2,3,4,5- tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol hemimaleate to the dopamine D₁ receptor in a concentration-dependent manner.