“The motivation to seek social contact may arise from either positive or negative emotional states, as social interaction can be rewarding and social isolation can be aversive. While ventral tegmental area (VTA) dopamine neurons may mediate social reward, a cellular substrate for the negative affective state of loneliness has remained elusive. Here, (the authors) identify a functional role for dopamine neurons in the dorsal raphe nucleus (DRN), in which (they) observe synaptic changes following acute social isolation. DRN dopamine neurons show increased activity upon social contact following isolation, revealed by in vivo calcium imaging. Optogenetic activation of DRN dopamine neurons increases social preference but causes place avoidance. Furthermore, these neurons are necessary for promoting rebound sociability following an acute period of isolation. Finally, the degree to which these neurons modulate behavior is predicted by social rank, together supporting a role for DRN dopamine neurons in mediating a loneliness-like state.”
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Matthews GA, Nieh EH, Vander Weele CM, Halbert SA, Pradhan RV, Yosafat AS, Glober GF, Izadmehr EM, Thomas RE, Lacy GD, Wildes CP, Ungless MA and Tye KM: Dorsal Raphe Dopamine Neurons Represent the Experience of Social Isolation. Cell 164(4): 617-631 (2016).
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http://www.ncbi.nlm.nih.gov/pubmed/26871628