Abstract

Erection is generally viewed as a reflex mechanism that can receive higher CNS influences. Paraplegic men who have lost reflex activity from the genital area are, therefore, treated as irreversibly impotent. However, the innervation of the male reproductive system suggests that two neural pathways innervate the genitals. In theory, the second (thoracic-lumbar) pathway should compensate for the loss of the first (sacral) pathway in cases of low spinal lesions. Clinical practice, however, ignores the TL pathway as a basis for treatment of spinal cord-injured men. This study used an animal model to demonstrate that the TL pathway could mediate penile responses in paraplegic rats. Eighty-five percent (85%) of spinal animals showed penile responses following hypothalamic (MPOA) stimulation despite a complete loss of peripheral erectile reflexes. These results not only have important implications from a clinical perspective, they further document the physiology of erection and support the view that erection is not a primary parasympathetic activity, but probably results from a sequence of sympathetic processes.