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Brain Res. 1998 Mar 30;788(1-2):104-10.

Regulation of G protein-mediated adenylyl cyclase in striatum and cortex of opiate-dependent and opiate withdrawing mice.

Author information

1
Department of Psychiatry and Human Behavior, Veterans Affairs Medical Center and Brown University School of Medicine, Providence, RI 02908, USA.

Abstract

Previous research has demonstrated that acute and chronic opiate treatment alters receptor- and postreceptor-mediated adenylyl cyclase activity. This study examined the regulation of G protein- and forskolin-mediated adenylyl cyclase activity in mouse striatum and cortex after short- and long-term opiate exposure. To directly measure adenylyl cyclase enzymatic activity, assays were done in the presence of catalytic site activator forskolin. To measure G protein-mediated adenylyl cyclase activity, assays were performed in the presence of non-hydrolyzable guanosine 5'-triphosphate (GTP) analogue, 5'-guanylyl-imidodiphosphate. Short-term in vitro morphine exposure produced reductions in forskolin-stimulated adenylyl cyclase activity in striatal and cortical tissues. Long-term morphine treatment in mice was performed via morphine- or placebo-pellet implantation for 72 h; this treatment has been shown to produce opiate dependence and withdrawal. In both opiate-dependent and opiate withdrawing mice (1 h post-naloxone induction), there were significant increases in G protein-mediated adenylyl cyclase activity in the striatum (vs. controls). In opiate-dependent mice, there was an decrease in G protein-mediated adenylyl cyclase activity in cortex. In opiate-dependent mice, there were no changes in forskolin-stimulated adenylyl cyclase in the striatum or cortex. Increases in striatal G protein-mediated adenylyl cyclase could represent a compensatory adaptation that opposes the persistent inhibition of adenylyl cyclase by chronic opiate treatment contributing to the expression of opiate dependence and withdrawal.

PMID:
9554971
DOI:
10.1016/s0006-8993(97)01524-2
[Indexed for MEDLINE]

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