Oxytocin protects against negative behavioral and autonomic consequences of long-term social isolation

Abstract

Positive social interactions and social support may protect against various forms of mental and physical illness, although the mechanisms for these effects are not well identified. The socially monogamous prairie vole, which--like humans--forms social bonds and displays high levels of parasympathetic activity, has provided a useful model for investigating neurobiological systems that mediate the consequences of sociality. In the present study, adult female prairie voles were exposed to social isolation or continued pairing with a female sibling (control conditions) for 4 weeks. During weeks 3 and 4 of this period, animals were administered oxytocin (20 microg/50 microl, s.c.) or saline vehicle (50 microl, s.c.) daily for a total of 14 days. In Experiment 1, autonomic parameters were recorded during and following isolation or pairing. Isolation (vs. pairing) significantly increased basal heart rate (HR) and reduced HR variability and vagal regulation of the heart; these changes in isolated animals were prevented with oxytocin administration. In Experiment 2, behaviors relevant to depression [sucrose intake and swimming in the forced swim test (FST)] were measured as a function of isolation. Isolation reduced sucrose intake and increased immobility in the FST; these behaviors also were prevented by oxytocin. Administration of oxytocin did not significantly alter cardiac, autonomic or behavioral responses of paired animals. These findings support the hypothesis that oxytocinergic mechanisms can protect against behavioral and cardiac dysfunction in response to chronic social stressors, and can provide insight into social influences on behavior and autonomic function in humans.

Figures

Fig. 1

Mean (+SEM) HR (Panel A), SDNN index (Panel B), and RSA amplitude (Panel C) in paired or isolated prairie voles administered daily oxytocin (OT; 20µ/50µl/vole, SC) or vehicle (V; 50µl/vole, SC) at baseline and following 4 weeks of isolation/pairing. *P<.05 vs. respective group values>#P<.05 vs. respective baseline value. Note the scale differences among the 3 panels.

Fig. 2

Mean (+SEM) HR prior to and following atropine administration (4mg/kg, IP) in paired or isolated prairie voles administered daily oxytocin (OT; 20µ/50µ/vole, SC) or vehicle (V; 50µ/vole, SC). *P<.05 vs. isolated paired and values at the same time point.>

Fig. 3

Mean (+SEM) water intake (Panel A), sucrose intake (Panel B), and sucrose preference (Panel C) in paired or isolated prairie voles administered daily oxytocin (OT; 20µ/50µ/vole, SC) or vehicle (V; 50µ/vole, SC) at baseline and following 4 weeks of isolation/pairing. *P<.05 vs. respective group values>#P<.05 vs. respective baseline value. Note the scale differences among the 3 panels.

Fig. 4

Mean (+SEM) immobility time during a 5-min FST in paired or isolated prairie voles administered daily oxytocin (OT; 20ug/50ul/vole, SC) or vehicle (V; 50ul/vole, SC). *P<.05 vs. isolated paired and values at the same time point.>