Neural mechanisms of female aggression: Implications on the oxytocin and vasopressin systems DISSERTATION ZUR ERLANGUNG DES DOKOTRGRADES DER NATURWISSENSCHAFTEN (DR. RER. NAT.) DER FAKULTÄT FÜR BIOLOGIE UND VORKLINISCHE MEDIZIN DER UNIVERSITÄT REGENSBURG vorgelegt von Vinícius Elias de Moura Oliveira aus Santo Antônio do Monte, Brasilien im Jahr 2020 Das Promotionsgesuch wurde eingereicht am: Die Arbeit wurde angeleitet von: Prof. Dr. rer. nat. Inga D. Neumann Unterschrift: Dissertation Durchgeführt am Institut für Zoologie der Universität Regensburg Lehrstuhl für Tierphysiologie und Neurobiologie unter Anleitung von Prof. Dr. rer. nat. Inga D. Neumann Table of Contents TABLE OF CONTENTS Summary ............................................................................................................................................... 1 1. General Introduction .................................................................................................................. 5 1.1. Aggression ............................................................................................................................... 5 1.2. Post-weaning social isolation and aggression ............................................................... 9 1.3. Neural circuits of aggression ............................................................................................ 10 1.3.1. The lateral septum as a gate for aggressive behavior ........................................... 14 1.4. Neurochemistry and neuroendocrinology of aggression ......................................... 15 1.4.1. The oxytocin and vasopressin systems and their role in modulating aggressive behavior ........................................................................................................................ 18 1.5. Sex differences in aggression: Female aggression .................................................... 23 1.6. Aims of the present thesis ................................................................................................. 27 1.6.1. Comparing the effects of PWSI on aggression across the sexes ....................... 27 1.6.2. Evaluating the role of the OXT and AVP systems on female aggression ......... 28 Chapter 2: Post-weaning social isolation exacerbates aggression in both sexes and affects the vasopressin and oxytocin system in a sex-specific manner ........................... 30 2.1. Introduction ............................................................................................................................ 30 2.2. Material and Methods .......................................................................................................... 32 Animals ............................................................................................................................................... 32 PWSI procedure and housing conditions .................................................................................. 32 Overview of experiments (Fig 2.1) ............................................................................................... 33 Resident and Female Intruder test ............................................................................................... 34 Elevated Plus-maze .......................................................................................................................... 35 Social Preference Test .................................................................................................................... 35 Social Discrimination Test ............................................................................................................. 36 In situ hybridization ......................................................................................................................... 37 Receptor autoradiography ............................................................................................................. 38 Statistical analyses .......................................................................................................................... 38 2.3. Results..................................................................................................................................... 39 PWSI does not affect body and adrenal weights ..................................................................... 39 PWSI increases aggression in both male and female rats .................................................... 39 PWSI impairs social discrimination, but not anxiety-like behavior or social preference ............................................................................................................................................................... 41 PWSI increases OXT, but not AVP mRNA expression ........................................................... 42 PWSI alters V1a and OXT receptor binding ............................................................................... 45 2.4. Discussion .............................................................................................................................. 46 2.5. Conclusion ............................................................................................................................. 51 Chapter 3: The oxytocin-vasopressin balance within the lateral septum determines aggression levels in virgin female rats ....................................................................................... 52 3.1. Introduction ............................................................................................................................ 52 3.2. Methods................................................................................................................................... 55 Ratlines and animal care ................................................................................................................ 55 Female Intruder test (FIT) ............................................................................................................... 56 Overview of the in-vivo experiments ........................................................................................... 57 Stereotaxic surgery .......................................................................................................................... 59 Receptor autoradiography ............................................................................................................. 60 ELISA for plasma corticosterone ................................................................................................. 61 Radioimmunoassay for OXT and AVP ........................................................................................ 61 Drugs and Viruses ............................................................................................................................ 61 Patch-Clamp....................................................................................................................................... 62 Perfusion ............................................................................................................................................ 63 Immunohistochemistry ................................................................................................................... 63 Statistics ............................................................................................................................................. 65 3.3. Results..................................................................................................................................... 66 Social isolation and training reliably enhanced female aggression ................................... 66 The high levels of aggression displayed by isolated and trained rats are underlined by high levels of OXT and low levels of V1a receptor binding .................................................. 68 OXT promoted whereas AVP reduced aggression in a central approach ......................... 70 The pro-aggressive effect of OXT was mediated in the vLS ................................................. 73 AVP exerted anti-aggressive effects within the dLS ............................................................... 76 Two distinct subregions of the LS are differently regulated by the activation of OXTRs ............................................................................................................................................................... 78 An intrinsic GABAergic circuit within the LS regulates female aggression ..................... 81 3.4. Discussion .............................................................................................................................. 84 4.1 General Discussion .............................................................................................................. 92 4.2 Outlook for PWSI .................................................................................................................. 95 4.3 Outlook for the IST protocol .............................................................................................. 98 4.4 Concluding remarks .......................................................................................................... 103 Abbreviation List ............................................................................................................................ 104 References ....................................................................................................................................... 106 Acknowledgments .........................................................................................................................