Abstract:

Abstract:Objective To examine the nerve connections of the sexually dimorphic nucleus of the preoptic area (SDN-POA) in the rat, and explore the function of  SDN-POA.Methods A total of 30 transgenic rats were used in the study，which expressed enhanced green fluorescent protein (EGFP) under the control of an estrogen receptor α gene promoter 0/B.The male and female rats (n=15, respectively) were randomly divided into three groups, and Fluoro-Ruby, a fluorescent tracer, was stereotaxically injected into the ventromedial hypothalamus (VMH), bed nucleus of the stria terminalis (BST) and posterodorsal nucleus of the amygdale (MePD) by iontophoresis, respectively.Five days later, the rats were perfused, and the sections containing SDN-POA region and site of injection were cut on a freezing microtome.the sections were viewed to assess extent of tracer deposition in the injection site and to reveal the EGFP or Fluoro-Ruby fluorescence in SDN-POA under fluorescence microscope.Results In male and female transgenic rats,  the cells labeled with EGFP were specifically distributed in the SDN-POA, and the volume and the number of cells in SDN were larger in the male than female and it demonstrated the sex difference.In the groups injected with tracer into the VMH and BST, the cells labeled with Fluoro-Ruby were determined in SDN.The labeled cells from VMH were distributed in the later of the SDN and the labeled cells from BST were dispersedly distributed in SDN in both sexes.In the group injected with tracer into the MePD, the labeled nerve fibers，not neurons，were discovered in SDN in both sexes.Conclusion SDN-POA is an important center nucleus to determine sexual dimorphism, and it would receive the afferent nerve fiber from MePD and send the efferent nerve fiber to VMN and BST to regulate reproductio
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Key words: sexually dimorphic nucleus of the preoptic area;sex differences;retrograde tracing study；Fluoro-Ruby