Social defeat stress increases expression of μ-opioid... : NeuroReport (original) (raw)

Molecular Neuroscience

Social defeat stress increases expression of μ-opioid receptor mRNA in rat ventral tegmental area

Nikulina, Ella M.1,5; Hammer, Ronald P. Jr.1,2; Miczek, Klaus A.1,2,3; Kream, Richard M.2,4

1Department of Psychiatry, Tufts University, New England Medical Center, NEMC Box 1007, 750 Washington St., Boston, MA 02111, USA

2Department of Pharmacology and Experimental Therapeutics, Tufts University, New England Medical Center, NEMC Box 1007, 750 Washington St., Boston, MA 02111, USA

3Department of Psychology, Tufts University, New England Medical Center, NEMC Box 1007, 750 Washington St., Boston, MA 02111, USA

4Department of Anesthesiology, Tufts University, New England Medical Center, NEMC Box 1007, 750 Washington St., Boston, MA 02111, USA

5Corresponding Author: Ella M. Nikulina

ACKNOWLEDGEMENTS: This research was supported by USPHS Awards DA09822, DA02632 and DA04128. The results were presented in part at the Society for Neuroscience Annual Meeting in Los Angeles in November, 1998.

Received 7 July 1999; accepted 5 August 1999

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Abstract

PROMPTED by previous studies linking social defeat stress to changes in opioid antinociception, we evaluated the expression of μ-opioid receptor (MOR)-encoding mRNA in selected rat brain areas as a function of this type of stress. Because opioids mediate significant regulatory activities of brain dopamine neurons, dopaminergic loci in the ventral tegmental area (VTA) and substantia nigra (SN) were selected for analysis. Within 30 min after social defeat stress, the level of MOR-encoding mRNA, as detected and quantified by in situ hybridization histochemistry, increased in the lateral VTA and this increase was present for at least 6 h. In contrast, defeat stress was without effect on the expression of MOR-encoding mRNA in the SN. These data suggest that stress-induced alteration of MOR-encoding mRNA expression in the VTA may be involved in the consequences of social defeat stress.

© 1999 Lippincott Williams & Wilkins, Inc.