title: Effects of social defeat on dopamine neurons in the ventral tegmental area in male and female California mice.
abstract: Dopamine neurons in the ventral tegmental area (VTA) have important functions related to rewards but are also activated in aversive contexts. Electrophysiology studies suggest that the degree to which VTA dopamine neurons respond to noxious stimuli is topographically organized across the dorsal-ventral extent. We used c-fos immunohistochemistry to examine the responses of VTA dopamine neurons in contexts of social defeat and social approach. Studying monogamous California mice (Peromyscus californicus) allowed us to observe the effects of social defeat on both males and females. Females exposed to three episodes of defeat, but not a single episode, had more tyrosine hydroxylase (TH)/c-fos-positive cells in the ventral (but not dorsal) VTA compared with controls. This observation suggests that repeated exposure to aversive contexts is necessary to trigger activation of VTA dopamine neurons. Defeat did not affect TH/c-fos colocalizations in males. We also examined the long-term effects of defeat on c-fos expression in a social interaction test. As previously reported, defeat reduced social interaction in females but not males. Surprisingly, there were no effects of defeat stress on TH/c-fos colocalizations in any subregion of the VTA. However, females had more TH/c-fos-positive cells than males across the entire VTA, and also had greater c-fos-positive cell counts in posterior subregions of the nucleus accumbens shell. Our results show that dopamine neurons in the VTA are more responsive to social contexts in females and that the ventral VTA in particular is sensitive to aversive contexts.
authors.affiliation: Neuroscience Graduate Group, University of California, Davis, CA, USA.|Department of Psychology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.|Center for Neuroscience, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Gian D
authors.initials: GD
authors.lastname: Greenberg
authors.affiliation: Department of Psychology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.|Molecular, Cellular and Integrative Physiology Graduate Group, University of California, Davis, CA, USA.
authors.forename: Michael Q
authors.initials: MQ
authors.lastname: Steinman
authors.affiliation: Department of Psychology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Ian E
authors.initials: IE
authors.lastname: Doig
authors.affiliation: Department of Psychology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hao
authors.affiliation: Neuroscience Graduate Group, University of California, Davis, CA, USA.|Department of Psychology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.|Center for Neuroscience, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Trainor
mesh_terms: D000818:Animals; D002452:Cell Count; D004291:Dominance-Subordination; D005260:Female; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009474:Neurons / Q000473:pathology / Q000502:physiology*; D010542:Peromyscus; D010784:Photomicrography; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011581:Psychological Tests; D012727:Sex Characteristics; D013315:Stress, Psychological / Q000473:pathology / Q000503:physiopathology*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D017557:Ventral Tegmental Area / Q000473:pathology / Q000503:physiopathology*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D014446:Tyrosine 3-Monooxygenase
keywords: behaviour; behavioural neuroscience; dopamine; sex differences; stress