Study On NNOS-Immunoreactive Nerve Terminals In The Prepuce And Frenulum Of The Penis

Objective: 1. To study the distribution of neuronal nitric oxide synthase (nNOS) immunoreactive nerve terminals in the prepuce and frenulum of penis in adult human and provide the theoretical reference for clinical circumcision. 2. To investigate the distribution of nNOS immunoreactive neurons in the dorsal root ganglia (DRG) and explore the role of nitric oxide (NO) in the producing and transmission of nociceptive information in the frenulum. Methods: 1. The nNOS-immunoreactive nerve terminals in the penile prepuce and frenulum in adult human and rat were detected by the method of immunohistochemistry. 2. The fluorogold (FG ) retrogradely tracing and nNOS immunofluorescence was used to tracing the origin of nNOS-immunoreactive terminals in frenular skin of rat penis. Results: 1. Using immunohistochemistry, the dense nNOS-immunoreactive nerve terminals distributing in a cluster were observed in the epidermal basal stratum of the penis prepuce and frenulum in adults. These nerve terminals were arborescent and beady in appearance. The density of these nerve terminals is significantly higher in frenulum than that in prepuce (P<0.01). 2. The dense nNOS-immunoreactive nerve terminals were observed in the epidermal basal stratum and papillary layer of dermis of the penile prepuce and frenulum in rats. These nerve terminals were arborescent and beady in appearance. 3. After injecting FG into the frenular skin, FG retrogradely labeled neurons were mainly localized in bilateral L6-DRG neurons and a few in S1-DRG neurons, FG positive-neurons were arranged in rows or spots among nerve bundles. Further FGtracing method combined with nNOS immunofluorescence indicated that a numble of DRG neurons were showed nNOS-immunoreactive. Most of nNOS-positive neurons were small-sized and a few were medium-sized. 41.2% and 41.3% FG-labeled neurons also have nNOS expression in L6-DRG and S1-DRG respectively. Except L6-DRG and S1-DRG neurons, no FG-labeled neuron were observed in L1-S4 spinal segments or in the rest of DRG neurons. Conclusions: 1. nNOS-immunoreactive nerve terminals were densely distributed in the prepuce and frenulum of human penis, the density of these nerve terminals is significantly higher in frenulum than that in prepuce. 2. The distribution of nNOS-immunoreactive nerve terminals in adult is similar to that in rat. 3. nNOS-immunoreactive nerve terminals of the frenulum were mainly originated from peripheral branches of neurons which express nNOS-positive immunoreaction in L6-S1 DRGs.