Calmodulin increases in selective brain regions with opioid dependence.

Acute challenge of thalamic membranes with opioid agonists displaces calcium and prevents isoproterenol stimulation of adenylate cyclase. Chronic morphine administration for three days or three weeks results in significant increases in the level of calmodulin in membranes of thalamus, but not in periaqueductal gray, striatum, amygdala or hypothalamus.