Aggressive encounters alter the activation of serotonergic neurons and the expression of 5-HT1A mRNA in the hamster dorsal raphe nucleus.

Full Abstract

Serotonergic (5-HT) neurons in the dorsal raphe nucleus (DRN) have been implicated in stress-induced changes in behavior. Previous research indicates that stressful stimuli activate 5-HT neurons in select subregions of the DRN. Uncontrollable stress is thought to sensitize 5-HT neurons in the DRN and allow for an exaggerated 5-HT response to future stimuli. In the current study, we tested the hypothesis that following aggressive encounters, losing male Syrian hamsters would exhibit increased c-Fos immunoreactivity in 5-HT DRN neurons compared to winners or controls. In addition, we tested the hypothesis that losers would have decreased 5-HT1A mRNA levels in the DRN compared to winners or controls. We found that a single 15-min aggressive encounter increased c-Fos expression in 5-HT and non-5-HT neurons in losers compared to winners and controls. The increased c-Fos expression in losers was restricted to ventral regions of the rostral DRN. We also found that four 5-min aggressive encounters reduced total 5-HT1A mRNA levels in the DRN in losers compared to winners and controls, and that differences in mRNA levels were not restricted to specific DRN subregions. These results suggest that social defeat activates neurons in select subregions of the DRN and reduces message for DRN 5-HT1A autoreceptors. Our results support the hypothesis that social stress can activate 5-HT neurons in the DRN, reduce 5-HT1A autoreceptor-mediated inhibition, and lead to hyperactivity of 5-HT neurons.

Author information

Author/s: Cooper, M A (MA); Grober, M S (MS); Nicholas, C R (CR); Huhman, K L (KL);

Affiliation: Department of Psychology, University of Tennessee, Knoxville, TN 37996-0900, USA. mcooper(-atsign-)utk.edu

Grants: F32 MH72085 (Agency:NIMH NIH HHS) ; MH62044 (Agency:NIMH NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.

Journal: Neuroscience (Neuroscience), published in United States. (Language: eng)

Reference: 2009-Jul; vol 161 (issue 3) : pp 680-90

Dates: Created 2009/06/01; Completed 2009/08/24;

PMID: 19362123, status: MEDLINE (last retrieved date: 8/24/2009)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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