Publication Date

2015

Document Type

Honors Thesis

Department

Neuroscience

Keywords

Microtus, Social behavior in animals, Oxytocin, Oxytocin-Receptors, Oxytocin-Psychological aspects, Septum (Brain), Amygdaloid body, Meadow voles, Social behavior, Lateral septum, Central amygdala

Abstract

As we strive to learn more about the biological basis of the human condition, it is important to look at the function of hormonal systems and their influence on behavior. The relationship between oxytocin (OT) and social behavior, for one, is complex and enigmatic, but meadow voles (Microtus pennsylvanicus) are particularly good models for studying forms of hormone-mediated sociality. In contrast to other monogamous vole species, they mate promiscuously, which is primarily associated with low oxytocin receptor (OTR) density in the nucleus accumbens in females (Anacker and Beery, 2013). While the role of OT in the formation of opposite-sex pair bonds has been well studied, less is known about its role in same-sex affiliative behaviors observed in vole populations. Female meadow voles are antisocial and aggressive toward each other during the mating season, but in the shorter, colder days of winter they tend to form social groups and huddle together for warmth. While OT in the nucleus accumbens seems to have little bearing on partner preference formation between same-sex animals the way it does between mated pairs, voles in their prosocial "winter" condition have significantly higher OTR densities in the central nucleus of the amygdala (CeA) than those living on a summer schedule (Beery and Zucker, 2010). The CeA has thus been implicated as a candidate region in which OT may be regulating same-sex social bonding behavior, along with the lateral septum (LS), in which OTR binding has a significant, negative correlation with huddling proclivity (Beery and Zucker, 2010). This study examines the effect of OT infusion in the LS and the CeA of female meadow voles on peer social behavior. Animals housed under prosocial "winter" conditions were cannulated and treated with infusions of oxytocin, oxytocin combined with an oxytocin receptor antagonist (OTRA), or artificial cerebrospinal fluid (aCSF) as the control. In the lateral septum infusion cohort, a fourth group treated with a vasopressin receptor antagonist (VRA) was also included after finding evidence of OT action outside the OTR. Following the infusion, focal animals were cohoused with another female of similar age for 24 hours, after which they underwent a partner preference test with the cagemate and a stranger. The lateral septum infusions showed that, compared to the typical partner preference demonstrated by the control animals, treatment with OT inhibited normal social bonding and resulted in an absence of partner preference, such that the animals spent equal time huddling with the cagemate partner as they did with a stranger. Simultaneous treatment with the OTRA did not attenuate these OT effects, but treatment with the VRA did, potentially indicating that OT is in fact acting upon V1a receptors instead of OTRs in the lateral septum. The CeA infusion component of this study is currently underway, but preliminary data suggest that bilateral OT infusion also prevents the demonstration of a partner preference, possibly by inhibiting the typical stress response to an "intruder" and thereby increasing stranger tolerance. Treatment with OTRA is expected to return huddling patterns to baseline, but it is too early yet to determine.

Language

English

Comments

47 pages : color illustrations. Honors project-Smith College, 2015. Includes bibliographical references (pages 45-47)

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