Distribution and source of calcitonin gene-related peptide immunoreactive nerve terminal in prepuce of penis and frenulum of prepuce of rats

Zhongmin WU; Donghong WANG; Lidong ZHAO; Shucai LING; Xi ZHU

ABSTRACT

BACKGROUND:

Frenulum of prepuce of penis contained many nerve terminals is an extremely sensitive region. If the frenulum is injured in circumcision or other operations, the complication, such as postoperative spontaneous pain of penis, sexual disturbance and so on, will occur. But there still is no define explanation for this up to now.

OBJECTIVE:

To observe the distribution of immunoreactive nerve terminal of calcitonin gene-related peptide (CGRP) in prepuce of penis and frenulum of prepuce of adult SD rats, and look for the source of CGRP immunoreactive nerve terminal in frenulum of prepuce.

DESIGN:

A single sample trial.

SETTING:

Department of Anatomy, School of Medicine, Zhejiang University.MATERIALS The experiment was performed at Department of Anatomy,School of Medicine. Zhejiang University from September 2004 to May 2005. A total of 20 adult male SD rats were selected, and were raised in warm, quiet, photophygous environment for 1 week before the trial so as to make the rats fit for the environment and maintain their basal state.

METHODS:

The rats were assigned randomly into 2 groups. Ten rats in the first group were treated with the immunohistochemical method to observe the distribution of CGRP immunoreactive nerve terminal in prepuce of penis and frenulum of prepuce of adult rats. Ten rats in the second group were treated with fluorogold (FG) retrograde labeled combined with CGRP immunofluorescence labeled method to look for the source of CGRP immunoreactive nerve terminal in frenulum of prepuce of penis. MAIN OUTCOME

MEASURES:

①The morphology and distribution of CGRP immunoreactive nerve terminal in prepuee of penis and frenulum of prepuce of adult SD rats were observed under light microscope. ②The distributive density and difference of CGRP immunoreactive nerve terminal in prepuce of penis and frenulum of prepuce were detected and compared (represented by A). ③Morphology and distribution of FG retrograde labeled -positive, CGRP single-labeled positive and FG/CGRP double-labeled positive neurons in dorsal root ganglion were observe under fluorescence microscope. ④Mean quantity of FG retrograde labeled positive, CGRP single abeled positive and FG/CGRP double-labeled positive neurons in dorsal root ganglion was counted.

RESULTS:

Totally 20 rats were involved in the analysis of results. ① Amber-coloured CGRP immunoreactive nerve terminal appeared in prepuce of penis and frenulum of prepuce of adult rats. These nerve terminal mainly occurred in basal layer of epidermis and papillary layer of dermis, distributed as twig shape or intestiniform; mostly of them were bundled, different in length, and some of them showed enlarged nodosity. ②The distributive density of CGRP immunoreactive nerve terminal in frenulum of prepuce of penis was significantly larger than that in prepuce of penis (2.15±0.32, 1.02±0.22,t =-2.03,P＜0.01). ③Combined with the FG retrograde labeled method it was found that these nerve terminal was derived from neurons of dorsal root ganglion opposed to the sixth lumbar spinal cord and the neurons of dorsal root ganglion opposed to the first acral spinal cord. FG retrograde labeled positive neurons differed in length. The cell body showed round or orbicular-ovate, without obvious prominence. Bright inaurate fine particle appeared in cytoplasm, no label in nucleus. Most cells arranged in line along nerve tract or diffusedly distributed. Most CGRP single-labeled positive neurons were middle or small cells found by CGRP immunofluorescence labeling. Dyeing was too dark.Reaction product distributed evenly in cytoplasm, which showed bright dark green (FITC labeled color). The same positive section was observed comparatively under different excitation light. It was found that FG/CGRP double-labeled positive cells were middle or small, and its amount accounted for a half of the total number of FG retrograde positive cells.

CONCLUSION:

CGRP may participate the transmission of sensory information in prepuce of penis and frenulum of prepuce of rats. The CGRP immunoreactive nerve terminal in frenulum of prepuce of penis of rats is sourced from neurons of dorsal root ganglion opposed to the sixth lumbar spinal cord and the neurons of dorsal root ganglion opposed to the first sacral spinal cord.