P3.32. SOCIAL BRAIN: THE ROLE OF RELAXIN-3 AND OXYTOCIN SYSTEMS IN REGULATING SOCIOSEXUAL BEHAVIOUR
Gabriela Czerniak1, Gabriela Stopka1,2, Kinga Przybylska1,2, Sylwia Drabik1,2, Patryk Sambak1,2, Anna Blasiak1
1 Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University, Cracow, Poland
2 Doctoral School of Exact and Natural Sciences, Jagiellonian University, Cracow, Poland
INTRODUCTION: The brainstem nucleus incertus (NI) plays a key role in stress, anxiety, and social interactions. It is the main source of the neuropeptide relaxin-3 (RLN3), which activates its receptor RXFP3. The NI sends dense RLN3ergic projections to the forebrain bed nucleus of the stria terminalis (BNST), a region critical for regulating anxiety, stress, and social and sexual behaviours. The BNST also shows high expression of oxytocin (OXT) receptor OXTR and RXFP3. However, the molecular profiles of the BNST and NI, especially regarding the RLN3/RXFP3 and OXT/OXTR systems and their roles in sociosexual behaviour, remain largely unknown.
AIM(S): The study aimed to elucidate the role of NI in sociosexual behaviour in male and female Spraque-Dawley rats. It sought to examine the distribution of RLN3-positive fibres in BNST and the sensitivity of BNST neurons to RLN3 administration.
METHOD(S): A sociosexual behavioural test was conducted, followed by c-Fos immunohistochemical staining in the NI. Viral-based anterograde tract tracing was used to identify the source of RLN3-ergic fibres in the BNST. Patch-clamp ex vivo recordings with RLN3 administration were performed on BNST neurons to assess their sensitivity to the peptide.
RESULTS: A greater density of c-Fos-positive cells was found in the NI of males that interacted with females, compared to control males, while no such difference was observed between experimental and control groups in females. RLN3-containing fibres from the NI were colocalized in the BNST. RLN3 administration during patch-clamp recordings induced a whole-cell outward current in BNST neurons.
CONCLUSIONS: These observations suggest the possible involvement of the NI in sociosexual behaviours control in males and indicate that the BNST remain under the influence of RLN3/RXFP3 and OXT/OXTR systems. The patch-clamp experiment provides evidence that the BNST is sensitive to RLN3 and that RLN3 has a pronounced inhibitory influence on its neuronal activity.
FINANCIAL SUPPORT: National_Science_Centre, Poland: UMO-2023/49/B/NZ4/01885, UMO-2018/30/E/NZ4/00687, UMO 2021/41/N/NZ4/04499