Immediate and Long-Term Effects of Tibial Nerve Stimulation on the Sexual Behavior of Female Rats

Objectives: There are limited treatment options for female sexual dysfunction (FSD). Percutaneous tibial nerve stimulation (PTNS) has shown improvements in FSD symptoms in neuromodulation clinical studies, but the direct effects on sexual function are not understood. This study evaluated the immediate and long-term effects of PTNS on sexual motivation and receptivity in a rat model of menopausal women. Our primary hypothesis was that long-term PTNS would yield greater changes in sexual behavior than short-term stimulation.

Materials and methods: In two experiments, after receiving treatment, we placed ovariectomized female rats in an operant chamber in which the female controls access to a male by nose poking. We used five treatment conditions, which were with or without PTNS and no, partial, or full hormone priming. In experiment 1, we rotated rats through each condition twice with behavioral testing immediately following treatment for ten weeks. In experiment 2, we committed rats to one condition for six weeks and tracked sexual behavior over time. We quantified sexual motivation and sexual receptivity with standard measures.

Results: No primary comparisons were significant in this study. In experiment 1, we observed increased sexual motivation but not receptivity immediately following PTNS with partial hormone priming, as compared with priming without PTNS (linear mixed effect models; initial latency [p = 0.34], inter-interval latency [p = 0.77], nose poke frequency [p = 0.084]; eight rats). In experiment 2, we observed trends of increased sexual receptivity (linear correlation for weekly group means; mounts [p = 0.094 for trendline], intromissions [p = 0.073], lordosis quotient [p = 0.58], percent time spent with a male [p = 0.39], decreased percent time alone [p = 0.024]; four rats per condition), and some sexual motivation metrics (linear correlation for weekly group means; nose pokes per interval [p = 0.050], nose poke frequency [p = 0.039], decreased initial latency [p = 0.11]; four rats per condition) when PTNS was applied long-term with partial hormone priming, as compared with hormone-primed rats without stimulation.

Conclusions: PTNS combined with hormone priming shows potential for increasing sexual motivation in the short-term and sexual receptivity in the long-term in rats. Further studies are needed to examine variability in rat behavior and to investigate PTNS as a treatment for FSD in menopausal women.