| Due to the great success of zoogony and lactation, the mammals improve the survival rate and adaptability of their offspring, and gradually occupy the predominance in the whole kingdom, especially for human. However, the inter-dependence appears between the parents and their children, the parental care even continues to several years after birth of offspring in several species.So we know that enviroment factors in the early life,especially for the mather and father,play very important roles for the development of the pups.Maternal behaviors(MB)that is considered as a key investor not only offer abundant nutrition, but also beneficial social enviroments such as tactile stimulation, body temperature, protections et al. In addition to maternal care, the paternal behaviors(PB) have also been identified in the monogamous species. Mating-system is offen identified by partner preference, levels of biparental care, atttachment of the spouse and the duration of this bond in a breeding season on the same species. The OT and DA systems are essential in the pair bond formation and maintenance. In addition to the functions of uterine contraction and galactogogue action induced by OT, it is also proved as neurotransmitter involving in more physiological process, such as learning and memory, drug addiction, maternal behavior, sexual behavior et al. The formation and maintenance of pair bond is associated with the reward mechanism, the process of study and memory,and the mechanism of motivation and attention. Mating facilitate the formation of pair bond, and induce the release of DA in several species. Based on the above data, present study used mandarin voles,which is a socially monogamous rodents,as animal model to explore the following questions:1)the behavioural variation during the pair-bond formation of the adult voles postnatally cared by two parents under the lab enviroment;2)the behavioral variation during the pair-bond formation of the voles whose father is deprived under the lab environment, and behavioural difference through comparing with the voles from PC group; 3) the behavioural variation during the pair-bond formation of the voles who is isolated 3h daily during postnatal 0-13 in a incubator, and the difference through comparing with the voles from PC group; 4)the different neural response to stress of adult mandarin vole derived from different early life social enviroment; 5) the different levels of OTRmRNA and DA2RmRNA expression in NACC and Me in adult mandarin vole derived from different postnatal social enviroment on offsprings. Thus, we used mandarin vole with complex social behaviors, as animal model and established three early social environments in the present research, those are biparental care (PC), paternal deprivation (PD) and early social deprivation (ED). We observed the behaviours during the pair-bond formation of the adult offspring derived from different eary life enviroment,the neural response to stress and expression of OTR and DA2R mRNA in related brain regions.The main results include the following points:1.The adult mandarin voles from PC group during the pair bonding experiment,had reduced significantly aggressive behaviors,and increased significantly affinity behaviors both female and male;the female voles in this group increased the time of exploring enviroment,but the male voles in this group increased the inactive time.The comparative results between the both female and male in this variation showed that the aggression of the female voles were more than the male at day 0,and that the sniff behaviors of the male were more than the female,but the affinity of the female were more than the male at the third day.Partner preference formation and selective aggression were found both male and female mandarin voles in this group after 3 days mating and cohabitation.so we can conclude that the stable pair bond could formed on the mandarin voles for the parental care afte 3 days cohabitation.2.The mandarin vole offsprings whose father was deprived during the pair bonding experiment, increased significantly affinity behaviors both sexes,but the female voles in this group reduced the time of exploring enviroment and was not found aggression behaviors;the male voles in this group reduced significantly aggression behaviors and the inactive time.The comparative results between the both sexes in this variation showed that the aggression of the female voles were less than the male at day 0,and that the female groom behaviors for the male were more, the affinity of the female and male were both high,but not significant difference at the third day.In contrast to the parental group,the female voles in this group appeared less aggressive behaviors at the day O,the male voles between the two groups have not different.Partner preference formation and selective aggression were found both male and female mandarin voles in this group after 3 days mating and cohabitation.so we can conclude that the stable pair bond could formed on the mandarin voles for the parental care afte 3 days cohabitation.3.The mandarin voles who was isolated in the early life enviroment during the pair bonding experiment,decreased aggressive behaviors and inactive behaviors, and increased significantly affinity behaviors both sexes. The comparative results between the both sexes suggested that the aggressive behaviors between female and male were no difference at day 0;and that the female groom behaviors for the male were more,the affinity of the female and male were both high,but not significant difference at the third day.In contrast,the voles in this group increased dramatically the aggressive behavior in the female and male at day 0,and increased the affinity behaviors at day 3.In the Partner preference experiment, the female and male voles in this group appeared selective aggressive behaviors both,but without partner preference that the voles increased exploring and affinity in the strange box. Thus,the function of pair bonding for early life isolation were significant,which made the aggressive behaviors and affinity increased,and blocked the partner preference.4. Comparing to the PC group,the number of Fos-immunoreactive (Fos-IR) neurons in the brain region of the ED.dramatically increased in the PVN,BST and Ce in the female voles;dramatically increased in the PVN and BST in the male voles.Comparing to the PC group,the number of Fos-immunoreactive (Fos-IR) neurons in the brain region of the PD, significantly increased in the PVN and BST in the female;significantly icreased in the PVN, BST and Ce in the male voles.Thus,we suggested that ED and PD accelerated the stress activity in the mandarin voles.through had difference between the ED and PD,and sexual dimorphism.5. Comparing to the PC group,the expression of the OTmRNA and the DA2RmRNA in NACC,dramatically increased in the female voles and have no difference in the male voles of the ED group ;dramatically increased in the male voles and had no difference in the female voles of the PD group.Interestingly,the expression of the OTmRNA in Me among the PC,PD and ED group,showed significantly difference and had the similar trend between the female and male voles,the most in the PD group,and the second in the PC group,and the last one in the ED group. Thus,we suggested that different early life environment had important function on the relative receptor densities of regulating the pair bonding in associated brain region in the mandarin voles. |
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