Cataleptogenic doses of morphine suppress 3H-spiroperidol binding to striatal membranes.

The Scatchard analysis of 3H-spiroperidol binding to crude synaptosomal fraction of rat striatum has revealed that in rats receiving cataleptogenic doses of morphine the density, but not affinity of dopamine receptor is depressed. The effect is mediated through opiate receptor, as it is reversible with naloxone. The data support the idea that one population of receptors may regulate another receptor population, and may explain the mechanism of morphine-induced catalepsy and increase in striatal dopamine turnover.