Abstract: The close parent-infant bonding before weaning is critical in mammals, which facilitates the emotional attachment between each other. However, the mechanisms on filial emotional attachment towards a parent remain poorly understood. Arginine vasopressin (AVP) and corticosterone (CORT) play important roles in social interaction and social bonding. This study aimed to investigate the potential mechanisms on parent-induced attachment in ICR mice pups through conditioned place preference (CPP) test. We investigated place preference of pre-weanling male pups following four days′ maternal or paternal reinforcing, while the immunoreactive (IR) neurons of hypothalamic AVP and c-Fos were detected by immunohistochemistry staining. In parallel, the levels of serum CORT were detected by enzyme-linked immunosorbent assay in mice pups. The pups conditioned with a parent showed place preference for the chamber paired with dam or sire cue with a corresponding increase in c-Fos expression in the paraventricular nucleus of the hypothalamus (PVN) and a decrease in serum CORT levels compare to the pups conditioned with empty chamber (P<0.05), and the pups conditioned with dams displayed higher levels of AVP expression in the PVN (P<0.05). In comparison with the pups conditioned with sires, the pups conditioned with dams showed lower levels of PVN c-Fos expression (P<0.05) and serum CORT concentration (P<0.05). There were not significant differences in c-Fos-and AVP-IR expression in the supraoptic nucleus of the hypothalamus (SON)(P>0.05). These results indicate the pre-weanling pups display place preference when conditioning with mothers or fathers. The neuronal activation and AVP release in the PVN and alterations of serum CORT may contribute to a parent induced-preference, and there were some differences with respect to the neuroendocrine activities of pups between maternal and paternal conditioning.

Key words: ICR mice, place preference, arginine vasopressin, corticosterone, c-Fos