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 D1receptors. The aim of the present work was to find evidences for a probable interaction between this neuropeptide and the dopamine D1receptor 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 D1receptor in a concentration-dependent manner.