Postpartum Repeated Separations From Pups Affect Emotional And Social Behavior And Associated Neuroendocrine In Mandarin Vole(Microtus Mandarinus) Fathers

Depression is a most commonly mood disorder from which women are more likely to suffer after giving birth. At present, most studies focus on women postpartum depression, alterations in men mood during the postpartum are neglected. This study investigated the impact of short-term separation and long-term separation from pups on emotional and social behaviorand neuroendocrine of fathers using socially monogamous mandarin vole (Microtus mandarinus).30male and30female mandarin voles were divided into three groups:none pups separations (NPS), brief pups separations (BPS,15min/d), long pups separations (LPS,3h/d). Pups were isolated after postnatal2to14days. In the next day after weaning, the open-field test was, the social interaction test and the forced swimming test were conducted respectively with two days interval between two days. The levels of Fos expression were measured within30-45min after FST. The levels of central oxytocin (OT) and AVP expression in the paraventricular nucleus (PVN) and serum OT and corticosterone (CORT) were also measured using immunohistochemistry and Elisa methods. The main results were presented as following:1. In the open-field testWe observed significant difference among the three groups on the percentage of time in central area, total distance and transitions. The animals from BPS group spent significant less time in the central area than NPS and LPS group, and there is no difference between the NPS group and LPS group on percentage of time in central area. The animals from BPS group moved significantly less distances and crossed less frequently than the NPS and LPS group.2. In the male-male social interactionThe separation from pups significantly affected the total duration of many behaviors among the three groups. The frequency of attacks in the animal from LPS group was significantly less than the BPS and the NPS groups.3. In the forced swimming testFathers separated long time repeatedly from their pups spent significantly longer time keeping immobile than the normal fathers during forced swimming test. But there were no difference between the LPS and BPS group on this measurement.4. The OT-IR neurons The number of OT-IR neurons showed significant difference between the three groups. Both the LPS and BPS groups showed significantly more OT-IR in the PVN than NPS group. In addition, we found difference on the number of OT-IR neurons between LPS fathers and the BPS fathers.5. The AVP-IR neuronsThe LPS group showed significantly more AVP-IR neurons in PVN than NPS and BPS group. But there was no difference between BPS and NPS.6. The FOS-IR neuronsIn our study, fathers long-time separated repeatedly from their pups demonstrated more Fos-ir neurons in the bed nucleus of stria terminalis (BNST), hypothalamic paraventricular nucleus (PVN), medial amygdaloid nucleus (MeA), paraventricular nucleus of thalamus(pv) and medial preoptic area (MPOA). In the lateral septum(LS), only the LPS showed significant more Fos-ir neurons than the NPS. However, no overall significant differences were found in central amygdaloid nucleus (CeA) and supraoptic nucleus of the hypothalamus (SON) between three groups.7. OT levels in serumWe found that only repeated long separation from pups significantly up-regulated subsequent serum OT level of mandarin vole fathers.8. Corticosterone levels in serumThe separation from pups increased the concentration of serum corticosterone. Both the LPS and BPS groups showed higher concentration of serum corticosterone than those in the NPS group.The results suggest that isolation of postnatal pups increased levels of anxiety and depression in mandarin vole fathers showing time-dependent effects. These effects are possibly associated wiith the alteration in levels of central OT, AVP and the serum corticosterone.