FACILITATION AND INHIBITION OF THE URETHROGENITAL REFLEX IN SPINAL CORD-TRANSECTED RATS

It was evaluated in the spinal cord-transected rats whether the urethr ogenital (UG) reflex shows some of the features that are present durin g ejaculation in intact animals. It was found that the UG reflex was f acilitated after its first elicitation: the latency of the reflex was shorter than the previous one and low intensity of stimulation was nee ded to produce the reflex. In addition, a change in the latency of the reflex was found that was correlated with the number of stimulation t rials. The latency change showed a J-shaped curve that is similar to t hat found for the ejaculation latency in a copulatory series. An inhib ition of the reflex appeared after several trials: the reflex could no t be elicited after three continuous trials. The reflex could be elici ted again if the intensity of stimulation was increased. The UG reflex also showed 'exhaustion': it could not be elicited, even with high in tensities of stimulation. after 3 h of rest. All these findings were p resent when the UG reflex was elicited by applying pressure to the ure thra or when it was evoked by the electrical stimulation to the pudend al nerve. According to these findings, it can be concluded that the UG reflex maintains some of the features that are found during ejaculati on in intact animals. According to this view, it can be speculated tha t some of the mechanisms that control ejaculation in intact animals ca n be localized at a spinal level. (C) 1997 Elsevier Science B.V.