Lithium alters mu-opioid receptor expression in the rat brain

Lithium can potentiate the effects of antidepressant drugs and alters morph ine analgesia and phosphoinositide turnover. Analysis of mu-opioid receptor immunostaining after chronic lithium administration in rats revealed an in crease in the density of cells expressing mu-opioid receptors in the caudat us-putamen, the dentate gyrus, the lateral septum and the frontal, parietal and piriform cortices, These data suggest that mu-opioid receptor expressi on in the rat forebrain is altered by in vivo chronic lithium treatment. Th is could be a compensatory mechanism, induced in part by the effects of lit hium on mu-opioid receptor transduction mechanism. (C) 2000 Elsevier Scienc e Ireland Ltd. All rights reserved.