This research is concerned with the relation between certain reflexes, mediated at the level of the spinal cord, and their hypothetical inhibitory control by the brain. The experimental model employed is the male rat's mating behavior and its related reflexes. The major questions concern the neural basis of the reflex rhythmicity, the role of stimulation in altering reflex potential, the ontogeny of reflex potential and its neural and gonadal hormonal basis, and the location of brain structures that modulate spinal reflex potential.