Objective: Post-menopausal vaginal pain and burning sensation are not solely relieved by improving vaginal dryness. Stimulation of pain receptor (nociceptor) may be a part of the post-menopausal vaginal pain mechanism. The authors primarily evaluated the level of substance P receptor in pre- and post-menopausal women and secondarily studied the level of calcitonin gene-related peptide (CGRP) receptor and nociceptor-activating substances in pre- and post-menopausal women. The association between vaginal pain score and the change in nociceptor and nociceptoractivating substances was analyzed.

Materials and Methods: A cross-sectional study was conducted in 122 pre- and post-menopausal women that underwent total abdominal hysterectomy. Vaginal specimens were obtained and stained for substance P receptor, substance P, CGRP receptor and CGRP, which were used as nociceptive parameters in the present study. Vaginal stromal cells were counted for pain-related protein expressions. Mean pain-related protein expressions in vaginal stromal cells were compared between pre- and post-menopausal women.

Results: Fifty-eight pre-menopausal women and 33 post-menopausal women were included for analysis. Mean substance P receptor, substance P, CGRP receptor and CGRP in post-menopausal women were higher than in pre-menopausal women (47.69, 42.32, 71.31 and 60.73 cells, respectively for post-menopausal women, and 22.03, 21.54, 41.45 and 35.80 cells, respectively for pre-menopausal women). These differences were under the major influence of hormonal status rather than age. The changes in mean pain-related protein expression in vaginal stromal cell after menopause were highest in the first two years. No difference in mean pain-related protein expression in vaginal stromal cell was observed between pain and no pain groups.

Conclusion: In the present study, post-menopausal women were found to have higher mean pain-related protein expressions in vaginal stromal cells than pre-menopausal women.

Keywords: Post-menopausal women, Vaginal pain, Vaginal dryness, Vaginal burning sensation, Vaginal nerve, Substance P, CGRP, Calcitonin gene-related peptide

DOI: doi.org/10.35755/jmedassocthai.2021.03.11430

Received 25 May 2020 | Revised 17 October 2020 | Accepted 20 October 2020