Neural circuitry involved in sexual function.
Neurological injury results in devastating sexual deficits in both men and women. Effective treatment requires an understanding of the central nervous system (CNS) pathways and physiology. This article emphasizes the essential similarities in the pathways and physiology of sexual function in men and women. Literature review. Systems within the spinal cord are fully capable of generating a large number of sexual responses. Spinal sexual centers may be activated by genital afferents or by descending commands from higher CNS sites. Normal functioning probably involves activation of spinal centers by both descending pathways and afferent stimulation. Afferent stimulation also modulates the activity of supraspinal sites, creating a positive feedback system. Descending control consists of powerful inhibitory and excitatory pathways. An important serotonergic inhibitory pathway has been demonstrated. The medial preoptic region participates in the integration of hormonal and sensory cues necessary for sexual behavior. The medial amygdala and paraventricular nucleus of the hypothalamus also play essential excitatory roles. The paraventricular nucleus projects directly to relevant spinal sites, indicating another important pathway for excitatory control. Recent advances have markedly enhanced our understanding of the physiology, pharmacology, molecular biology and pathology of sexual mechanisms. This knowledge base is essential in order to understand changes in sexual mechanisms that follow spinal cord injury, and for the development of effective interventions to maximize sexual function in men and women with spinal cord injury.