RNAi knockdown of oxytocin receptor in the nucleus accumbens inhibits social attachment and parental care in monogamous female prairie voles

Abstract

Oxytocin modulates many aspects of social cognition and behaviors, including maternal nurturing, social recognition and bonding. Natural variation in oxytocin receptor (OXTR) density in the nucleus accumbens (NAcc) is associated with variation in alloparental behavior, and artificially enhancing OXTR expression in the NAcc enhances alloparental behavior and pair bonding in socially monogamous prairie voles. Furthermore, infusion of an OXTR antagonist into the NAcc inhibits alloparental behavior and partner preference formation. However, antagonists can promiscuously interact with other neuropeptide receptors. To directly examine the role of OXTR signaling in social bonding, we used RNA interference to selectively knockdown, but not eliminate, OXTR in the NAcc of female prairie voles and examined the impact on social behaviors. Using an adeno-associated viral vector expressing a short hairpin RNA (shRNA) targeting Oxtr mRNA, we reduced accumbal OXTR density in female prairie voles from juvenile age through adulthood. Females receiving the shRNA vector displayed a significant reduction in alloparental behavior and disrupted partner preference formation. These are the first direct demonstrations that OXTR plays a critical role in alloparental behavior and adult social attachment, and suggest that natural variation in OXTR expression in this region alone can create variation in social behavior.

Keywords: Alloparental care; Pair bonding; Striatum.

Figure 1

In vivo Knockdown of prairie vole OXTR expression. Twenty-one day old females were injected with an AAV virus expressing a shRNA targeting Oxtr mRNA (shRNA-pvOxtr) or targeting a scrambled sequence (scrambled Oxtr control). Receptor autoradiography showing OXTR density in the nucleus accumbens (NAcc), caudate putamen (CP) and prefrontal cortex (PFC) of females injected with (A) scrambled Oxtr control or (B) shRNA-pvOxtr. Expression of the shRNA expressing virus did not damage neurons as both the scrambled Oxtr control (C) and shRNA-pvOxtr (D) treated females expressed the green fluorescent protein. (E) shRNA-pvOxtr females expressed approximately 45% less OXTR binding than scrambled Oxtr control females. Asterisk represents a p-value less than 0.05. Data are represented as mean ± SEM. Scale bar, 1 mm.

Figure 2

Graph showing the effect of OXTR knockdown on alloparental behavior. (A) Scrambled Oxtr control females spend more time licking and grooming pups than shRNA-pvOxtr females. (B) Scrambled Oxtr control females showed normal variation in propensity to engage in alloparental behavior, with about 60% showing spontaneous nurturing care. However, shRNA-pvOxtr females displayed inhibited alloparental care, indicating that decreased OXTR expression in the NAcc is directly related to decrease alloparental behavior. Asterisk represents a p-value less than 0.05. Data are represented as mean ± SEM.

Figure 3

Partner preference behavior in shRNA-pvOxtr and scrambled Oxtr control females at 70 days old treated at 21 days old. (A) After 24 hours cohabitation period and mating, only the scrambled Oxtr control females displayed a significant preference for the partner over the stranger. (B) After 24 hours cohabitation period and mating, there were no differences in locomotor behavior. Asterisk represents a p-value less than 0.05. Data are represented as mean ± SEM.