Some proposals regarding the organization of the central nervous system control of penile erection

Recent research on the central nervous control of penile erection is discus sed. A framework for this control is based upon principles put forward by F rank Beach regarding the neuroendocrine regulation of male copulatory behav ior. The current discussion is focused primarily on a subset, penile erecti on, The spinal cord contains all the necessary components for the productio n of penile erection. This requires a multisegmental coordination among pen ile vasodilator and vasoconstrictor autonomic neurons, pudendal motoneurons responsible for penile rigidity and autonomic neurons which control extra- penile blood flow. Genital sensory stimulation can activate this spinal net work. The spinal cord is also under excitatory and inhibitory control from supraspinal sites. Penile erection can be driven by supraspinal input alone and supraspinal control can inhibit the erectile effects of genital stimul ation. An important aspect of the CNS control of penile erection is that there are extensive interconnections between most of the brain sites identified to d ate, Most of the pathways are characterized by reciprocal connections, A la rge number of the CNS sites also receive genital sensory information. Thus, descending control may itself be modulated by ascending sensory pathways w hich relay information from the genitalia. This raises the possibility that penile erection may involve a positive feedback system. Receptors for gona dal hormones have been identified throughout the neuraxis. However, strong evidence for the control of male sexual function by gonadal hormones has be en identified only for forebrain sites. The functional role of brainstem an d spinal gonadal hormone receptors has not yet been clarified. (C) 2000 Els evier Science Ltd. All rights reserved.