| kisspeptin is a kind of neuropeptide of the retinoic acid family, which is synthesized by the tumor suppressor gene (kiss-1). It widely distributed in the brain hypothalamic dorsomedial nucleus, the solitary tract nucleus and the tail of the ventrolateral medulla. In2003, results showed that it involved in the regulation of reproduction. Neurokinin B (NKB) is a kind of tachykinin, which widely distributed in the central and peripheral nerve tissue. Recently, papers reported that NKB also played an important role in normal function of puberty.Many studies have confirmed that kisspeptin can stimulate the animal to release the gonadotropin,while the similar reports about NKB are rare. In the current study,to explore the variation of phase and space of the kisspeptin/NKB in the hypothalamus, immunofluorescence and laser confocal microscspy were used to observe the location of kisspeptin/NKB in the hypothalamus of rats. The concentrations of sex hormone and kisspeptin/NKB in the serum were detected by radioimmunoassay and ELISA respectively.The results will provide some morphological evidence to clarify their roles and mechamism in the start of pubertyThe results showed that (1) kisspeptin immunopositive cells were mainly found on the ventromedial hypothalamic nucleus,arcuate nucleus and paraventricular nucleus which were different degrees of expression.①emale rats:The expression intensity of kisspeptin in the ventromedial hypothalamic nucleus, arcuate nucleusin (ARC) female rats at infancy age was significantly higher than that in the newborn period (P<0.05)、prepuberty (P <0.05), puberty (P<0.05) and adulthood (P<0.05); the expression intensity in these parts except paraventricular nucleus in puberty was significantly higher than that of in newborn period (P<0.05), proestrus (P<0.05) and adulthood (P<0.05); the expression intensity between the prepuberty and adulthood period was no significant difference(p>0.05); The highest expression intensity in childhood was arcuate nucleus, followed by the ventromedial nucleus; the expression intensity in ventromedial nuclear of puberty was significantly higher than that of in ARC (P<0.05), paraventricular nucleus (P<0.05) and the anterior (p<0.05).②ale rats:The highest expression intensity in arcuate nucleus was found in male rats in prepuberty, followed by infancy period, puberty and adulthood; the significant differences of the expression intensity in ventromedial nucleus was not found between infancy period and puberty (p>0.05),but both of them were significantly higher than that of in newborn period(p<0.05), prepuberty (P<0.05) and adulthood (P <0.05); the expression intensity in paraventricular nucleus in puberty was significantly higher than that of in newborn period (p<0.05), childhood (p<0.05), prepuberty (P<0.05) and adulthood (p<0.05); the expression intensity between ventromedial nucleus and ARC was not found in puberty,but both of them were significantly higher than paraventricular nucleus (P<0.05) and preoptic area (P<0.05).(2) The expression of NKB in female rats was similar to kisspeptin, however, the location was not the same. Overall, the expression intensity of NKB was a little higher than kisspeptin.①female rats:The expression intensity in the ventromedial nucleus in and ARC of childhood was significantly higher than that of the newborn period (P<0.05), prepuberty (P<0.05), puberty (P<0.05) and adulthood (P<0.05); the expression intensity in the ventromedial nucleus in and paraventricular nucleus of puberty was significantly higher than newborn period (p<0.05), prepuberty (P<0.05) and adulthood (P<0.05); the expression intensity in ARC of puberty was significantly lower than prepuberty (P<0.05) and significantly higher than the other three periods; the expression intensity in arcuate nucleus of prepuberty was significantly higher the ventromedial nucleus in (P<0.05) and paraventricular nucleus (P<0.05); the expression intensity in ARC of adulthood was significantly lower the ventromedial nucleus in (P<0.05) and paraventricular nucleus (P<0.05).②ale rats:the expression intensity of NKB in those parts of puberty was significantly higher than the newborn period (P <0.05), childhood (p<0.05), prepuberty (P<0.05) and adulthood (p<0.05); the expression intensity in the ARC of newborn was significantly higher than the newborn period (P <0.05), prepuberty (P<0.05) and adulthood (P<0.05); the significant difference of the expression intensity in these parts was not found between prepuberty and childhood (P>0.05;(3) The serum concentration of kisspeptin/NKB was not different significantly.(4)The serum concentration of estradiol was low in newborn and childhood,while the maximum serum concentration of estradiol was found in prepuberty rats, then it decreased gradually; The lowest serum concentration of testosterone was seen in childhood and puberty, and there was not significant difference (P>0.05); the maximum serum concentration of testosterone was found in adulthood, followed by puberty.It made the conclusion:(1)We found the high expression of kisspeptin in the hypothalamus of female rats at childhood and puberty, while the high intensity of expression was in arcuate nucleus of male rats at prepuberty and in the hypothalamus of male rats at puberty. Overall, the expression of kisspeptin in the hypothalamus of female rats was higher than the that of male rats, suggesting that there were sex differences in the regulation of rat reproductive start time.(2)There was not significant differences between the expression intensity of NKB in the hypothalamus of female and male rats, while he expression intensity was high at childhood and puberty. However the expression intensity of male rats at puberty was higher than that at childhood, suggesting there were sex differences in the regulation of rat reproductive start time.(3) The difference of the concentration of kisspeptin/NKB in serum was not significant during the growth and development of rats, suggesting kisspeptin/NKB was expressed in the hypothalamus and played a role.(4)The maximum serum concentration of Estradiol was found in early puberty rats, then it decreased gradually,while the trends of the last three periods were generally opposite to the serum concentration of kisspeptin; the maximum serum concentration of testosterone was found in adult male rats, while the trends were similar to the serum concentration of NKB,suggesting kisspeptin/NKB played a role in the starting of puberty. |
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