Involvement of neuropeptidergic neurons in the establishment of dominance in a teleost model of non-breeding aggression: neuropeptide-specific and status-dependent actions

Abstract

Abstract The establishment of the dominant-subordinate status implies a clear behavioral asymmetry between contenders that arises immediately after the resolution of the agonistic encounter and persists during the maintenance of stable dominance hierarchies. Changes in the activity of the brain social behavior network (SBN) are postulated to be responsible for the establishment and maintenance of the dominant-subordinate status. The hypothalamic nonapeptides of the vasopressin/vasotocin (AVP/AVT) and oxytocin/mesotocin/isotocin (OXT/MST/IT) family are known to modulate the activity of the SBN in a context-dependent manner across vertebrates, including status-dependent modulations. We searched for status-dependent asymmetries in AVT/IT cell number and activation immediately after the establishment of dominance in the weakly electric fish, Gymnotus omarorum, which displays the best understood example of non-breeding territorial aggression among teleosts. We used immunolabeling (FOS, AVT, and IT) of preoptic area (POA) neurons after careful designed intermale dyadic agonistic encounters. We show for the first time in teleosts, that AVT, but not IT, is involved in the establishment of the dominant-subordinate status. We also found status-dependent POA subregion-specific changes of AVT cell number and activation that confirm the involvement of AVT in the establishment of dominance likely achieved by the release of AVT from dominants’ AVT neurons.