Identification of a vaginal pacemaker: An immunohistochemical and morphometric study.

Vaginal electric waves spread caudally in the vagina. We investigated the hypothesis that electric waves originate from a centre of interstitial cells of Cajal (ICCs) in the proximal vagina. Specimens (0.75 x 0.75 cm) were obtained from the vaginal walls of 23 cadavers (age 38.2 +/- 10.2 years). Sections were prepared for immunohistochemical investigations using the specific ICC marker, C-kit. Morphometric studies for image analysis using a Leica imaging system were performed. C-kit positive cells were detected in vaginal smooth muscle. Results from image analyser revealed that mean area percent of positive immunoreactivity for C-kit in the upper part of posterior vaginal wall was significantly higher (p < 0.0001) than of areas in other vaginal walls, and also significantly higher (p < 0.05) in circular than in longitudinal muscle layer. Studies have shown that the greatest collection of ICCs occurred in the upper part of the posterior vaginal wall. The vaginal electric waves are suggested to originate from this 'centre' and spread caudally.