Long-term adaptation to high doses of morphine causes desensitization of mu-OR- and delta-OR-stimulated G-protein response in forebrain cortex but does not decrease the amount of G-protein alpha subunits.

Abstract

Prolonged exposure of rats to high doses of morphine results in decrease of the over-all output of OR-stimulated G-protein activity in the forebrain cortex but does not decrease the amount of these regulatory proteins. These data support the view that the mechanism of the long-term adaptation to high doses of morphine is primarily based on desensitization of OR-response preferentially oriented to mu-OR and delta-OR.