Effects of bromocriptine on receptor binding of methionine-enkephalin

Bromocriptine inhibited the binding of methionine-enkephalin (ENK) to rat striatal synaptic membranes in a dose-dependent fashion. The bromocriptine IC50 was 16 micrometers. hill coefficients of bromocriptine were 0.7 and 0.3, suggesting that an allosteric effect was involved in bromocriptine inhibition of ENK binding to its receptor. These data suggest that at least a part of the therapeutic antiparkinsonian effect f bromocriptine is its allosteric effects on the ENK receptor, which influences the function of striatal dopamine neurons and/or of striatal cholinergic neurons.