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.