Oxytocin and affiliative behavior in prairie voles Open Access

Ross, Heather (2009)

Permanent URL: https://etd.library.emory.edu/concern/etds/2f75r874m?locale=en
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Abstract

Abstract Oxytocin and affiliative behavior in prairie voles By Heather E. Ross

Oxytocin is produced in the hypothalamus and released into the circulation through the neurohypophyseal system. Peripherally released oxytocin facilitates parturition and lactation. Centrally released oxytocin plays a role in maternal nurturing behavior and affiliative behavior in adults. Oxytocin receptors in the nucleus accumbens have been implicated in the regulation of alloparental behavior and pair bond formation in the socially monogamous prairie vole. There are both interspecies differences in oxytocin receptor density in the nucleus accumbens of monogamous and non-monogamous prairie voles, as well as, individual differences within prairie voles, that are functionally related to differences in affiliative behaviors. Here we show that the distribution of oxytocin- immunoreactive fibers in the nucleus accumbens is conserved in prairie voles, mice and rats, despite remarkable species differences in oxytocin receptor expression in the region. However, the origin of these accumbal OT fibers is unknown. Using a combination of site-specific and peripheral infusions of the retrograde tracer, Fluorogold, we demonstrate that oxytocin-immunoreactive fibers in the nucleus accumbens likely originate from paraventricular and supraoptic hypothalamic neurons. This distribution of retrogradely labeled neurons is consistent with the hypothesis that striatal oxytocin fibers arise from collaterals of magnocellular neurons of the neurohypophysial system. If correct, this may serve to coordinate peripheral and central release of oxytocin with appropriate behavioral responses associated with reproduction, including pair bonding after mating, and maternal responsiveness following parturition and during lactation. In addition, we used adeno-associated viral vector gene transfer to examine the functional relationship between accumbal oxytocin receptor density and social behavior in prairie and meadow voles. Adult female prairie voles that over-express oxytocin receptor in the nucleus accumbens displayed accelerated partner preference formation after cohabitation with a male, but did not display enhanced alloparental behavior. However, partner preference was not facilitated in non-monogamous meadow voles by introducing oxytocin receptor into the nucleus accumbens. These data are the first to demonstrate a direct relationship between oxytocin receptor density in the nucleus accumbens and variation in social attachment behaviors. Thus, individual variation in oxytocin receptor expression in the striatum may contribute to natural diversity in social behaviors.

Table of Contents

TABLE OF CONTENTS CHAPTER 1: GENERAL INTRODUCTION

1.1 Introduction 2 1.2 Coordinating Birth and Parental Care 3 1.3 Maternal Care in Rodents 4 1.4 Maternal Bonding in Sheep 7 1.5 Alloparental Behavior in Voles 9 1.6 Pup-Mother Interactions 12 1.7 Social Bonding in Adults 14 1.8 Social Recognition in Rodents 19 1.9 Social Cognition in Humans 22 1.10 Mediation of the Positive Effects of Social Support: stress 23 responses and immune function 1.11 Human Social Relationships 25 1.12 Neural Circuitry of the Oxytocin System 27 1.13 Characterization of Oxytocin Cells 27 1.14 Oxytocin Fibers of the Nucleus Accumbens 31 1.15 Conclusions 32 1.16 Dissertation Goals 32 CHAPTER 2: VARIATION IN OXYTOCIN RECEPTOR DENSITY IN THE NUCLEUS ACCUMBENS HAS DIFFERENTIAL EFFECTS ON AFFILIATIVE BEHAVIORS IN MONOGAMOUS AND POLYGAMOUS VOLES 2.1 Abstract 35 2.2 Introduction 36

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