RESUMEN
Objective To study the distribution and origin of calcitonin gene-related peptide(CGRP) immunoreactive nerve terminals in the prepuce and frenulum of penis of human and mice. Methods The CGRP-immunoreactive nerve terminals in the prepuce and frenulum of penis were detected by the method of immunohistochemistry.The fluoro-gold(FG) retrogradely tracing and CGRP immunofluorescence were used to tracing the origin of CGRP-immunoreactive terminals in the penile frenulum of rats. Results In the prepuce and frenulum of adult penis,CGRP-immunoreactive nerve terminals were mainly observed in the basal stratum and spinal stratum of epidermis distributing in a cluster.These nerve terminals were arborescent and beady in appearance.The density of these nerve terminals was significantly higher in frenulum than that in prepuce.The distribution of CGRP-immunoreactive nerve terminals in rats was similar to that of in adult.FG retrogradely tracing method found that the FG retrolabelled neurons were localized in L-6DRG and S-1-DRG.Combined CGRP immunofluorescence method indicated that a number of DRG neurons were showed CGRP-immunoreactive.CGRP-positive neurons were mainly moderate or small-sized,intense immunostained,bright green granules appeared as FITC fluorescence in the cytoplasm.These positive-neurons were arranged in rows or spots among nerve bundles.A half of FG-labelled neurons also showed CGRP-immunoreactive expression in L-6-DRG and S-1-DRG respectively.All of FG/CGRP double-labelled neurons were moderate or small-sized.Conclusion Large numbers of CGRP-immunoreactive nerve terminals were observed in the penile frenulum of human and rats.These terminals were originated from the peripheral branches of CGRP-immunoreactive neurons in L-6-DRG and S-1-DRG of rats.It is suggested that CGRP may take part in the transmission of nociception in the prepuce and frenulum of penis.