The role of monoaminergic nuclei during aggression and sympathetic social signaling

A social sign stimulus that is sympathetically induced affects aggressive a pproaches and influences serotonergic, dopaminergic and noradrenergic activ ity in the brainstem nuclei of Anolis carolinensis. Darkening of postorbita l skin via sympathetic activation of adrenal catecholamines and beta (2)-ad renergic receptors provides a visual signal that forms more rapidly in domi nant than subordinate males during social interactions. This signal limits aggressive interactions. Males were painted post-orbitally with green or bl ack paint and then exposed to a mirror. Aggressive approaches to the mirror were inhibited in males viewing a reflection with darkened eyespots, and i ncreased in males viewing a reflection without eyespots (hidden). Noradrene rgic turnover in the raphe and locus ceruleus were greatest in test subject s that viewed a reflection with eyespots hidden by green paint. Perception of darkened eyespots stimulated greater serotonergic turnover in raphe, loc us ceruleus and substantia nigra/ventral tegmental area (SN/VTA). Dopaminer gic turnover was higher in the raphe and SN/VTA of Anolis that viewed a ref lection with darkened eyespots. However, these animals had lower dopamine t urnover in the locus ceruleus than isolated and hidden eyespot groups. Of t he possible roles of perikarya on central function and behavior, our result s suggest feedback, cross-nuclear regulation, and some independence of func tion between nuclei and the forebrain terminal fields. Decreased serotonerg ic activity corresponds with increased aggression only in the raphe, sugges ting that the raphe nuclei might be important for this behavioral trait. In creased serotonergic, noradrenergic and dopaminergic activities in SN/VTA i n Anolis that view a reflected opponent with dark eyespots suggests that th e SN/VTA might be directly involved in recognition of this social sign stim ulus and the resulting inhibition of aggression. Copyright (C) 2001 S, Karg er AG, Basel.