In addition to impacting central systems, SSRIs may affect sexual functioning by acting on the peripheral vascular system (Frohlich & Meston, 2000). Evidence suggests that serotonin produces vasoconstriction and increased blood pressure by acting primarily on the 5-HT 2 and vasodilation by acting primarily on the 5-HT 1. Since SSRIs alter CNS 5-HT 1 and 5-HT 2 receptor activity it is feasible that SSRIs also alter peripheral 5-HT 1 and 5-HT 2 receptor activity. If so, sexual functioning could be impaired directly by affecting vasocongestion to the genital tissue or indirectly by altering sensory functions, such as tactile sensation, that have been found to be affected by hypertension. To examine this hypothesis, we (Frohlich & Meston, 2005a) conducted the first empirical examination of tactile sensitivity in women with and without female sexual arousal disorder. Tactile sensitivity was examined on the distal portion of the dominant hand index finger and on the lower lip. Finger threshold was significantly associated with severity of arousal dysfunction. Logistic regression showed that 76.5% of participants were correctly classified as functional or dysfunctional and 23.5% were incorrectly classified using tactile sensation as a predictor variable.
In a second study (Frohlich & Meston, 2005b), we examined whether SSRI-induced sexual difficulties arise in part from an over-sensitivity or under-sensitivity of tactile sensation. Tactile sensitivity was examined in clinically depressed women at baseline (pre-medication), week 1, week 4, and week 8 of fluoxetine treatment. Fluoxetine treatment resulted in decreased orgasm functioning that was not mediated by tactile sensation. An independent association was found between sexual arousal functioning and finger sensation, such that as sexual desire decreased, finger threshold increased.
Recommended paper:
Frohlich, P. F., & Meston, C. M. (2000). Evidence that serotonin affects female sexual functioning via peripheral mechanisms. Physiology & Behavior, 71(3-4), 383-393. (PDF 3.34 MB)
