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In some mammals, offspring may live with their parents for a very long time after weaning, but little is known about the effect of post-weaning parent-offspring cohabitation on the behavioral and neurobiological development of offspring. Here, we explored the effect of this experience on partner preference in adult mandarin vole (Microtus mandarinus). Levels of central oxytocin (OT), tyrosine hydroxylase (TH), as well as OT receptor (OTR), dopamine D1-type and D2-type receptors (D1R and D2R) mRNA expression in the nucleus accumbens (NAcc) and medial amygdala (MeA) were also measured. Our data showed that post-weaning living with parents inhibited the preference to partner over an unfamiliar opposite-sex conspecific. Voles with this experience possessed more OT-but less TH-immunoreactive neurons as compared to the control. Additionally, males with this experience had less D2R and OTR mRNA expression in the NAcc than the control while females had less D2R mRNA expression in the NAcc, but more OTR mRNA expression in the MeA. These findings demonstrate that post-weaning parent-offspring cohabitation inhibits the partner preference formation at adulthood, and these changes may be associated with alterations in the levels of central OT and DA, and their receptor mRNA expression in specific brain regions. [ABSTRACT FROM AUTHOR]

The socially monogamous mandarin vole ( Microtus mandarinus) shows significant behavioral plasticity. We examined whether levels of sociability, parental care and central expression of estrogen receptor alpha differed between two populations with different ecologies. Our results show that males from the Chengcun population display significantly more amicable and less aggressive behaviors towards novel same-sex individuals compared to males from the second population of Xinzheng. Chengcun voles directed more licking behavior towards neonatal pups than did Xinzheng voles. Differences were also found in the number of estrogen receptor alpha-immunoreactive neurons. For example, Xinzheng males displayed significantly higher immunoreactivity than Chengcun males in the medial amygdala, medial preoptic area and ventromedial nucleus of the hypothalamus. Xinzheng females expressed higher levels of estrogen receptor alpha-immunoreactivity than Chengcun females in the medial preoptic area. Chengcun females exhibited significantly more estrogen receptor alpha expression than Xinzheng females in the bed nucleus of the stria terminalis. Our results indicate that mandarin voles from the Chengcun site possess monogamous traits, and animals from Xinzheng possess polygamous traits. It also appears that different social behavior and levels of parental care in these two populations may be associated with differences in estrogen receptor alpha-immunoreactive neurons. [ABSTRACT FROM AUTHOR]