Effect of Light on Hypothalamic-Pituitary-Gonadal Axis in Young Female Golden Hamster
Objective To explore the effects of light intensity and duration on the hypothalamic-pituitary-gonadal(HPG)axis in female golden hamster pups.Methods Totally 30 female golden hamsters of 2 days old were randomly divided into normal group(12 h/50 lux),dim-light group(16 h/50 lux)and strong-light group(16 h/350 lux)according to a random number table,with 10 in each group.Animals in each group were exposed to the above light from 2 days of age until 28 days of age.Hamsters'general conditions and gonads were observed.The levels of sex hormones in peripheral blood and mRNA of gonadotrophin releasing hormone(GnRH),gonadotrophin Inhibiting hormone(GnIH)and melatonin receptor(Mel1c)in hypothalamus,G protein-coupled receptor 147(GRP147)and gonadotrophin releasing hormone receptor(GnRHR)in pituitary,and GnRHR in uterus and ovary were detected.Results In a certain range,as the light time extended and light intensity improved,compared with the normal group,hamsters in the dim-light and strong-light group showed obvious restlessness and were in an irritable state.Hamsters'skin glossiness in the two light groups was significantly worse,food intake and drinking water decreased.Compared with the normal group,the weight gains,levels of serum estradiol(E2)and hypothalamic Mel1c mRNA decreased in the strong-light group and the dim-light group(P＜0.05);thickness of myometrium decreased in the strong-light group(P＜0.01),and the level of hypothalamic GnIH mRNA increased in the strong-light group(P＜0.01).Wet weights of uterus and ovary,uterine index and GnRHR mRNA levels of pituitary and ovary in strong-light group decreased compared with those in dim-low light group(P＜0.05).Conclusion Prolonged exposure to strong light within a certain range after birth can lead to signs of Yin deficiency and Fire prosperity in female golden hamster pups,it also inhibits the energy metabolism and the synthesis of pituitary melatonin receptor mRNA as well as the functions of HPG axis to some extent.
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