Genital sensory feedback and sexual behaviour in male and female marmosets (Callithrix jacchus)

Local anaesthesia (using lidocaine) of the penis, or of the vagina and cervix caused marked changes in the sexual behaviour of marmosets. Penile desensitization did not affect sexual arousal or erectile capacity. However, intromission latencies increased and 7 out of 10 males failed to intromit during some post-lidocaine tests. Females failed to show several behavioural patterns which normally occur during intromission (shrugging body movements, head turning and opening the mouth) or exhibited them at reduced frequencies after intra-vaginal application of lidocaine. The tendency of females to terminate mounts after ejaculation had occurred was also reduced with resultant increases in intromission duration in all cases. Desensitization of the females' external genitalia had no effect upon sexual behaviour. Co-ordination of copulatory behaviour in this primate species depends, in part, upon afferent stimuli from the penis and from the vagina or cervix.