ALTERATIONS IN IMMEDIATE-EARLY GENE PROTEINS IN THE RAT FOREBRAIN INDUCED BY ACUTE MORPHINE INJECTION

Injection of morphine (10 mg/kg) induced a complex immediate-early gen e response in the rat forebrain, as detected with immunocytochemistry. The c-Fos protein was induced consistently in the dorsomedial caudate -putamen, the nucleus accumbens, and in midline and intralaminar nucle i of the thalamus. In some rats induction was also seen in the parieta l and insular cortex and in lateral regions of the caudate-putamen, In duction was detectable, although weak, at 30 min, was maximal at 2 h, and was undetectable 3 h after injection. JunB was induced in the same regions of the caudate-putamen as found for c-Fos, but was not induce d in the nucleus accumbens or thalamus. In the caudate-putamen, JunB i nduction was still present 3 h after injection. A considerably smaller induction of c-Jun was noted in the dorsomedial caudate-putamen and i n deep neocortex. Expression of JunD was inhibited in intralaminar and midline thalamic nuclei. Increases in numbers of cells immunoreactive for a Jun-related antigen (Jra) were found in the caudate-putamen and nucleus accumbens. These results indicate a complex immediate-early g ene response to acute morphine, suggesting that morphine activates or inhibits specific neurons and circuits in the forebrain.