Meeting Abstract
Neurokinin B, encoded by the tackykinin3 gene, is one of many neurohormones that work together to tightly regulate the reproductive axis. While previous research has mainly focused on tac3 for its role in regulating reproductive endocrinology, it remains unknown if tac3-cells are activated during social interactions or if tac3 expression is regulated by social state. To investigate how tac3 expression varies with social and reproductive status in the African cichlid fish Astatotilapia burtoni, we used in situ hybridization to map and quantify tac3 expression in the brains of dominant and subordinate males and ovulated and mouthbrooding females. Tac3-expressing cells were found in 20 different brain nuclei, and it was differentially expressed in approximately half of those regions. Dominant males had more tac3-expressing cells in the Vs, TPp, NLT, and PVO than subordinate males, and mouthbrooding females had more tac3 cells in the NLT than gravid females, potentially due to estrogen feedback. In addition, dominant males and ovulated females had scattered cells in many socially-relevant telencephalic nuclei (e.g. Dm, Dlg, Vd), but these tac3-expressing cells were absent in subordinate males and brooding females. Double labeling for the immediate early gene cfos and tac3 in the brains of fish collected after specific behavioral scenarios (i.e. spawning, territory defense) will determine whether any tac3 cell populations are activated during social interactions. To our knowledge, no study has examined the role of tac3 in social behaviors in fishes despite its known importance to the reproductive axis. Because expression differs with physiological state, it is possible that tac3 has reproductive state-dependent neuromodulatory effects in mediating complex social behaviors such as territoriality and reproduction.
