Sexual behavior is regulated by multiple neuroendocrine systems that influence each other in a dynamic interplay throughout the lifespan. During puberty, gonadal steroids drive reproductive maturation and play an essential role in the development of genital perception and responsiveness to touch. They also modulate sexual motivation and desire during adulthood. Thus, hormonal changes are crucial for both normal sexual development and sexual functioning.
Prolonged and excessive exposure to these hormones can have long-term effects on sensory pathways involved in sexual experience, affecting sexual response and pleasure. This happens through several mechanisms, such as alterations in gene expression, epigenetic modifications, and synaptic plasticity. In this article, I will discuss how prolonged hormonal changes induce lasting alterations in genital sensory pathways and sexual experience.
1) Gonadal steroids and the development of genital sensory pathways
During fetal life, the embryo develops external sex organs from undifferentiated mesenchymal tissues under the influence of testosterone or estrogen. The female fetus responds to high levels of estrogen produced by the placenta, whereas the male fetus produces low amounts of it until the testis begins to secrete androgens. Hormones control the differentiation of primary sex characteristics like the clitoris and penis and the formation of the urethra and vagina.
2) Genital responses to touch:
The skin is rich in nerve endings that detect light tactile stimulation and transmit information to the central nervous system. During puberty, estradiol increases the number of estrogen receptors (ERα and ERβ) expressed in peripheral sensory neurons responsible for genital sensation. These hormone receptors regulate the release of neurotransmitters like glutamate and substance P, which mediates the perception of touch and pain. Estrogen also affects the excitability of genital afferents by modulating potassium channels and ion fluxes.
3) Sexual motivation and behavior:
Gonadal steroids influence sexual desire and arousal throughout adulthood. In women, estradiol enhances sexual response by increasing libido and sexual pleasure. In men, testosterone stimulates sexual behavior and erectile function. Both hormones promote the expression of dopamine and oxytocin receptors in the hypothalamus, amygdala, and brain areas involved in sexual motivation and reward. They also increase blood flow to the genitalia, causing genital engorgement during arousal and erection.
Prolonged exposure to gonadal steroids can lead to hypersensitivity or desensitization to these hormones and loss of sexual interest. This may occur due to adaptive changes in the brain's reward circuitry caused by repeated exposure to high levels of dopamine.
4) Long-term effects on sensory pathways and sexual experience:
Excessive estrogen exposure can induce hyperplasia of genital nerve fibers, leading to increased sensitivity to light tactile stimulation (hyperesthesia). This can cause discomfort and painful genital sensations that reduce sexual satisfaction. Prolonged testosterone exposure has opposite effects, reducing the number of nerves and altering their responsiveness to touch (hypoesthesia). It also affects neurotransmitter release and ion fluxes, decreasing genital sensitivity and sexual pleasure. These long-term changes in genital sensory pathways persist even after hormonal fluctuations subside.
How do prolonged hormonal changes induce lasting alterations in genital sensory pathways and sexual experience?
The process of becoming an adult includes physical and mental development that involves various physiological transformations such as puberty. The onset of puberty is marked by the sudden production of sex hormones like testosterone and estrogen that cause physical changes related to sexual maturation. These changes also have profound effects on neural circuitry and functioning associated with sexual arousal, which are often long-lasting even after the cessation of hormonal activity.