Effects of chronic morphinization on calcium membrane interaction.

Tolerance to morphine proceeds with an adaptation in the nerve membrane causing an increase in endogenously bound calcium. Our data on calcium binding is compatible with Collier's hypothesis (10) for drug induced changes in number and/or types of receptors. The results demonstrating naloxone reversal of this membrane adaptation suggest that opiate antagonist action may be to maintain the opiate macromolecule portion of the membrane in a Ca++ associated homeostatic state. Lack of effects of Na+ on opiate treated SPM suggest that cellular adaptation to morphine proceeds in vivo through a change in membrane binding of calcium.