| Many experimental evidences indicate that abnormal steroid hormones levels in perinatal periods(at the end of gestation and shortly after birth) may affect sexual dimorphisms in brain and behavior during development,which induce abnormal sexual orientation and social behavior in adult. Estrogen receptor-a is primarily involved in masculinization,while estrogen receptor-βhas a major role in defeninization of sexual orientation and sexual behavior.They are two independent neural processes.Mandarin vole(Microtus mandarinus),who is high socially monogamous rodent,has become impromant animal mode of sexual behavioral nurobiology.Immediately after birth,male pups received a single dose of an antiestrogen—clomiphene citrate in order to establish a male homosexual model.At adulthood,sexual partner preference was tested to whether the male homosexual animal model was succeded.Using behavior observation methods,we investigated the effects of eonatal C6272 administration on sexual partner preference and prosocial behavior.In addition,we investigate the expression of ERαbetween neonatal males treated with C6272 and saline in different period(PN15,PN45 and PN60) by immunocytochemistry method to indicate the developmental mechanism of sexual orientation and sexual preference.Our results were the following:1.In order to explore the mechanism of social behavior regulated by estrogen in the brain and the effects of estrogen receptor alpha(ERα) on social and reproductive behaviors of mandarin vole(Microtus mandarinus),the distribution of ERαwas examined in the brain of adult male and female mandarin voles by immunocytochemistry method.The results showed that the ERα-IR was mainly localized in ARC,MeA,Ce,MPOA,VMH and BST.Distribution of ERαwas sexually dimorphic in the BST,MPOA,MeA and Ce,with females expressing significantly more ERα-IR cells than males(P＜0.01).Male mandarin voles expressed more ERα-IR in the ARC than females (P＜0.05).There were no significant differences in the VMH between two sexes(P＞0.05).These findings suggest that the distribution of ERαdiffers between male and female mandarin voles,which may cause the sexual differences of reproductive behavior and other social behaviors in mandarin voles.This sexual difference also may be one of the neural mechanisms that induce the monogamous social behaviors in this species.2.Immediately after birth,male pups received a single dose of an antiestrogen—clomiphene citrate. At adulthood,they were tested on sexual partner preference with a sexually experienced male stimulus animal and a stimulus estrous female.In comparison to saline treatment males,neonatal antiestrogen exposed males showed a sexual partner preference for the sexually active male as demonstrated by a negative partner preference score,more and longer visits to the male's compartment(0.01＜P＜0.05),fewer and shorter visits to the female's compartment (0.01＜P＜0.05).These results suggest that neonatal antiestrogen administration could affect the formation of male topic sexual orientation and make male show the same sexual partner preference and some female sexual behavior.All these data indicate that male homosexual model can be established by neonatal antiestrogen administration.3.Immediately after birth,male pups received a single dose of an antiestrogen—clomiphene citrate. At adulthood,they were tested on affiliative behavior and other social behavior with a sexually experienced male stimulus animal and a stimulus estrous female.The results showed that neonatal C6272 administration could increase the total number and the visiting duration of the aggression, defensive behavior and nonsocial behavior to the sexually active male,while decrease the total number and the visiting duration of the amicable behavior and investigating behavior to the sexually active male and the estrous female.The decrease of the total number and the visiting duration to the sexually active male and the estrous female mainly attributed to the reduction of "postive" social interactions.It is suggest that neonatal C6272 administration could reduce the expression of male prosocial behavior by up-regulating the expression of ERαin the male mandarin vole.4.Male mandarin voles were treated with C6272 for the first day of life and then tested in adulthood for sexual partner preferences.The distribution of ERαwas examined within one hour after the behavior tests by immunocytochemistry method.The results showed that males treated with C6272 expressed significantly more ERαin MPO,Me and Ce than control males(P＜0.05).Males treated with C6272 expressed less ERαin MPO,BST,Me and Ce than contral females(P＜0.05).In ARC, males treated with C6272 expressed more ERαthan contral femles(P＜0.05).There were no significant difference in the VMH between males treated with C6272 and control females.These findings suggest that the levels of ERαin males treated with C6272 is between the control males and control females.The absence of estrogen increased the expression of ERαin neonatal males,which made the male don't have a masculinized brain.As a result,male mandarin voles diplayed less male behavior and more female-like behavior.At the same time,the increased expression of ERαreduced the prosocial behavior and increased the aggressive behavior in the males treated with C6272.5.The expression of ERαwas examined between neonatal males treated with C6272 and saline in (different period(PN15,PN45 and PN60) by immunocytochemistry method.The results showed that males treated with C6272 expressed significantly more ERαin MPO,BST,Me and Ce than control males(P＜0.05).There were no significant difference in the VMH and ARC between males treated... |
PDF Full Text Request