The Effects of Melanotan II on the Social Network Properties in a Group of Male Rhesus Macaques: A Pilot Study Open Access

Kelley, Sean Walter (2016)

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Oxytocin (OT) is associated with a wide variety of prosocial behaviors including empathy, trust, cooperation, eye gaze and social vigilance. Most current research utilizes either intranasal or aerosolized OT, however it is unknown whether intranasal OT can cross the blood brain barrier. Melanotan II (MTII) is a non-selective melanocortin 4 receptor agonist that can potentially circumvent this problem by increasing endogenous OT in the brain. Our study looked at the effects of MTII (1 mg/kg) on the social network structure of a group of ten male rhesus macaques (Macaca mulatta) over two weeks. During the first week, half of the group received MTII and the other half received a placebo; the treatments were reversed the following week. In the third week no treatment was administered in order to establish a baseline social network. We collected a total of 5 hours of MTII/placebo data and 4.5 hours of baseline data. Coders used simultaneous focal sampling to record all instances of proximity and grooming behaviors for each monkey, which were then used to construct social networks. Using social network analysis (SNA), we examined the effects of MTI on four social network metrics: betweenness centrality, closeness centrality, eigenvector centrality and the clustering coefficient. MTII caused a significant increase in the closeness centrality as well as a significant decrease in the frequency of grooming given. Consequently, MTII monkeys were more likely to receive grooming from a greater number of monkeys and less likely to groom than placebo monkeys.

Table of Contents

Introduction 1

Aims and Hypotheses 7

Methods 11

Experimental Design 11

Data Analysis 13

Results 19

Proximity Duration 19

Total Proximity Behavior 19

SNA Measures 20

Grooming Received 24

Duration 24

Frequency 25

Grooming Given 26

Duration 26

Frequency 27

Grooming Duration: SNA Measures 28

Grooming Frequency: SNA Measures 31

Discussion 35

Anxiety 36

Locomotion 37

Limitations/Future Studies 38

MTII Effects on Prosocial Behavior 38

References 39

Appendix: SNA Measures 43

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