| The correct expression of maternal behavior plays an important role in the survival and healthy growth of offspring,and the positive interaction between mother and child can promote the normal development of offspring brain.Pregnancy stress is a common risk factor for postpartum mental disorders,which not only has adverse effects on the mother herself,but also reduces the quality of postpartum maternal behavior,which in turn damages the development of the offspring’s brain and psychological functions,resulting in cognitive,emotional and social dysfunction of the offspring.At present,less attention has been paid to how maternal behavior and psychological function change after experiencing pregnancy stress,and the intergenerational effect that pregnancy stress disrupts maternal nursing behavior and thus impairs offspring psychological and behavioral function.Studying the mechanism of stress disruption is conducive to better prevention and intervention of stress.For postpartum depression,although psychopharmacological intervention is an important aspect of treatment,nonpharmacological interventions also play a key role in this population.More importantly,pregnant and postpartum women tend to prefer non-drug interventions because of concerns about transplacental and lactation transfer.At present,there are relatively few studies on the improvement or treatment of postpartum depression by non-drug intervention,and whether it can improve maternal behavior after stress and whether this effect has cross-generational effect remains to be explored.Therefore,this study will explore the destructive effect of social stress during pregnancy on maternal behavior of postpartum maternal rat and the influence of maternal behavior disruption on offspring,and further explore the intervention effect of social interaction on this basis.Study 1 explored the effects of social stress during pregnancy on maternal sexual behavior and mental function in rats(Experiment 1),and further explored the effects of maternal stress on the mental function of offspring(Experiment 2).In experiment 1,postpartum depression was induced by the paradigm of social frustration stress during pregnancy,which was divided into direct stress and indirect stress.The direct stress was the direct contact between dams and male strangers for 10 minutes,and the indirect stress was the indirect threat for 2 hours after male strangers were placed in the cage and then in the cage of female rats.All dams were tested for maternal behavior in cages(PPD 3),pups preference test(PPD 4),open field test(PPD 5),elevated plus maze pups retrieval test(PPD 6),and forced swimming test(PPD 7).The animals used in experiment 2 were all the offspring of dams from experiment 1,and all the offspring were tested by social preference test(PND 36),novel object recognition test(PND 37),elevated plus maze test(PND 38)and forced swimming test(PND 39).The results showed that:(1)Social stress during pregnancy caused worse nursing behavior in postpartum rats,which showed that dams spent less time in active maternal behaviors,such as licking and crouching.(2)Maternal stress reduces offspring’s social preference.In object and peer preference tests,maternal stress reduces offspring’s social preference.(3)The anxiety-like behavior of the offspring was different between the sexes,and the anxiety level of the female offspring was significantly lower than that of the male offspring.Study 2 was designed to assess the ameliorating effect of social interaction on maternal behavior impaired by pregnancy stress(Experiment 3),and the ameliorating effect of maternal social interaction experience on offspring mental function(Experiment 4).In experiment 3,postpartum depression was induced by social frustration stress during pregnancy.The specific operation was the same as that in experiment 1.Social interaction paradigm was used to provide social support to dams.All dams were tested for maternal behavior in cages(PPD 3),pups preference test(PPD4),open field test(PPD 5),elevated plus maze pups retrieval test(PPD 6),and forced swimming test(PPD 7).The animals used in experiment 4 were all the offspring of dams in experiment 3.All the offspring were tested in social game behavior test(PND36),social preference test(PND 37),novel object recognition test(PND 38),object texture recognition test(PND 39),elevated plus maze test(PND 40)and forced swimming test(PND 41).The results showed that:(1)Under normal conditions,social interaction experience prolonged the incubation period of dams to retrieve their first pups,and gestational stress reduced the time that dams stayed with their pups;(2)Under stress conditions,the experience of social interaction can reduce the time of upright exploration of dams,and lead to a significant increase in the anxiety level of dams,and produce obvious anxiety-like behavior;(3)Maternal social interaction experience increases the time of progeny’s social exploration,improves the rats of texture recognition of objects,and increases the time of exploring peers in the social preference test;(4)Maternal stress causes offspring to spend less time exploring new objects and show lower recognition rates of new objects in new object recognition tests;(5)Under normal conditions,maternal experience of social interaction reduces the amount of time progeny spend rigor mortis in forced swimming.The above results showed that:(1)Social stress during pregnancy had adverse effects on the positive maternal behavior and anxiety level of maternal rats,and social interaction intervention could improve the non-maternal behavior of stressed maternal rats;(2)The effects of stress and social interaction have intergenerational effects.Maternal stress can reduce offspring’s social willingness and ability to recognize and remember new objects,while maternal social interaction experience can improve this negative effect.The results of this study further explain the destructive effects of gestational stress on maternal behavior and psychological function in rats,and reveal the intergenerational effects of maternal social interaction intervention on stress destructive maternal behavior and maternal social interaction intervention on maternal stress offspring psychological function.This will provide enlightenment for the intervention and treatment of postpartum mental diseases,and ultimately promote the health of mother and offspring. |
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