Differential activation of vasotocin neurons in contexts that elicit aggression and courtship

•Egr-1 expression in the preoptic area of Astatotilapia burtoni males is greater after fighting than after courting.•A greater proportion of AVT cells are positive for egr-1 mRNA after fighting than after courting.•Frequency of courting behaviors correlated with circulating 11-ketotestosterone levels.•We present the first report of v1a1 mRNA expression in the brain of a cichlid fish.•Expression patterns of AVT V1a-subtype receptors v1a1 and v1a2 in the brain overlap.

Despite continued study on the neurobiological bases of aggressive and sexual behaviors, it is still not well understood how the brain integrates social information with physiological and neural states to produce context-specific behavioral outcomes. In fishes, manipulation of endogenous levels of arginine vasotocin (AVT) through peripheral and intracerebroventricular pharmacological injections results in significant changes in social behaviors, including aggressive and reproduction-related behaviors. In addition, many features of AVT neurons have been shown to correlate with social status and associated behavioral phenotypes. In this study, we used the immediate early gene egr-1 as a marker for neuronal activity and quantified the number of AVT neurons that were positive for egr-1 mRNA by in situ hybridization in Astatotilapia burtoni males that were exposed to either a social context that would elicit aggression or to one that would elicit courtship. In these social settings, focal males readily displayed context- appropriate bouts of aggression (towards the opponent) or bouts of courting (towards females). We found that males that fought had higher levels of egr-1 expression in the preoptic area compared to courting males. A greater proportion of AVT cells was positive for egr-1 after a fight than after a bout of courting. We mapped mRNA distribution of AVT V1a receptor subtypes v1a1 and v1a2 in the brain and identified overlapping areas of expression in nuclei in the ventral telencephalon, hypothalamus and thalamus as key areas for AVT signaling in males.