Mandarin Vole Wild Populations Of Two Geographic Behavior And Brain Estrogen Receptor ¦Á Of A Comparative Study

The neuroendocrine system can regulate genesis and evolution of individual behaviours, while individual behaviours also can affect the function of the neuroendocrine system in a certain extent. Mating systems, as the expression of breeding behaviors, resulted from evolution with species-specific aspects and hereditability. Thus, differences in mating systems might be based on diversity of physiological procedures. The different populations of the same speices of voles displayed different social behaviours and neuroendocrine characters of different mating systems. But the neuroendocrine mechanisms of the different mating systems and different social behaviours is not clear. The previous research on behaviour patterns and neuroendocrine mechanisms of the mating systems of rodents focused on oxytocin (OT) and vasopressin (AVP). The regulations of the neurohypophyseal peptides is very important. The distribution patterns of OT and AVP recepters in brains of monogamous and polygamous vole species were evidently different. However, OT and AVP did not elucidate the mechanisms of monogamous evolution sufficiently. The research on polygamous rodents indicated that not only the neurohypophyseal peptides. but also estrogen (E) can regulate the behviors of males. Furthermore, E can regulate many behaviors that regulated by OT and AVP including partner preference, aggressive behaviors and parental care directly. In addition, E can decrease male's behaviors and increase the prosocial behavior of monogamy. So E may play an important role in evolution of monogamy. There were interspecific differences in the mating systems of voles. And voles with different mating systems had different neuroendocrine mechanisms. So voles were the ideal animal model of neroendocrinology. The behaviors related to the mating systems and the distribution patterns of ERαin brains in wild-caught Mandarin voles (Microtus mandarinus) from two populations with different altitudes and annual rainfalls were not clear. The purpose of the present research was to clarify more neuroendocrine mechanisms of behaviors related to the mating systems.Body mass, anxiety, locomotor activity, social interaction, partner preference and parental care of the two populations were compared. At the same time, the distribution patterns of estrogen alaph receptors (ERα) in BST, MeA, MPOA, ArC and VMH also were compared using immunocytochemistry. The main results were following.1. Xinzheng males were significantly heavier than Chengcun males. This showed that Xinzheng males may have greater intensity of sexual selection compared with Chengcun males. So it is infered that Xinzheng males may occupied more females and displayed nonmonogamous traits on body weight.2. Voles in the Chengcun population spent a significantly longer period of time in the central area of an open field compared with animals in the Xinzheng population, thereby demonstrating less anxiety in the Chengcun population. In addition. Chengcun males showed less aggressive behavior and more amicable behavior compared with Xinzheng males. Chengcun males and females might be able to form partner preferences after 72 h of cohabitation, while Xinzheng population was not able to form such preferences under the same condition. In the parental care test, the paternal care of Chengcun males has increase trend.3. Distribution of ERαin Chengcun population was sexually dimorphic in the MeA,MPOA,BST and the VMH with females expressing significantly more ERα-IR cells than males. While distribution of ERαin Xinzheng population was not sexually dimorphic in MeA,ARC,BST and VMH, but showed sexual dimorphis in the MPOA. Xinzheng males expressed significantly more ERα-IR cells than Chengcun males in the MeA,MPOA and the VMH.And Xinzheng females expressed significantly more ERα-IR cells than Chengcun females in the MPOA. These results indicated that the distribution of ERαin Chengcun population showed monogamous character, while the distribution of ERαin Xinzheng population showed polygamous traits.In conclution. these data suggest that the two populations show significant differences in body weight, anxiety, social interaction, partner preference and parental care. And Chengcun population demonstrated socially monogamous characteristics, but Xinzheng population displayed nonmonogamous traits. The different annual rainfall may influence food distribution, and furthermore, food distribution may affect population densities. Population density is accossiated with social organization. So the two populations displayed behaviors of different mating systems and social organizations. In addititon. there were different distribution patterns of ERαin brains in two populations of madarin voles. The distribution patterns of ERα-IR in Chengcun population showed monogamous patterns, while, the distribution patterns of ERα-IR in Xinzheng population displayed polygamous patterns. The different distribution of ERα-IR cells may cause the behavior variations in different population and different sexual Mandarin voles. And the variation of distribution patterns of ERαin intraspecific variation and intersexual variation may be one of the neuroendocrine mechanisms of social behaviors related to the mating systems.