Sensory control of the male rat's copulatory thrusting patterns.

The effects of reduced somatosensory feedback from the penis and/or the preputial region upon the male rat's copulatory thrusting patterns and sexual behavior were analyzed. Copulatory thrusting was recorded with an accelerometric technique allowing for the determination of duration and frequency of the thrusting trains. Section of the dorsal penile nerves (denervation) or lidocaine applied to the distal part of the penis reduced the number of intromissions and the intromission ratio. These treatments had no effect on copulatory thrusting patterns. Lidocaine injected into the preputial region also reduced the number of intromissions and the intromission ratio. Moreover, the number of disorganized mounts, as revealed by the accelerometric record, was much increased by this treatment. In addition, the duration of the thrusting trains associated with mount and intromission was increased. No effect was found on thrusting frequency. These data suggest that somatosensory feedback from the penis is critical for the achievement of intromission, whereas feedback from the preputial region is important for the execution of copulatory thrusting. Furthermore, it is possible that the strong sensory stimulation of the prepuce associated with penile insertion participates in the termination of thrusting and penile withdrawal.