Relation of autogrooming to sexual behavior in male rats

Abstract

Grooming and penile reflexes were studied in male rats that were restrained in supine position with the penile sheath retracted or were free to copulate with sexually receptive females. In Experiment 1 there was a reliable concordance in supine males between the tendency to groom and the tendency to display penile reflexes. In Experiment 2 we analyzed the sequential organization of grooming and genital events in supine tests. It was assumed that many or most episodes of ventral grooming would have been genital grooming had access to the genitalia not been prevented by restraint. Paw grooming tended to precede clusters of penile responses, whereas ventral grooming started after the onset of erections. Experiment 3 was an exploration of grooming in the context of copulation, rather than supine restraint. Males groomed their genitalia immediately after all intromissions and after all mounts that ended mount bouts. The duration of grooming was not affected by whether or not intromission occured. Finally, in Experiment 4 we observed genital and nongenital grooming and recorded electromyographic (EMG) activity from the striated bulbospongiosus muscle (mBS) of the penis in freely moving rats. Consistently, mBS activity led to genital grooming with a short latency, whereas nongenital grooming rarely led to genital grooming, and EMG activity was not associated with nongenital grooming nor did it tend to follow after genital grooming was initiated. The four experiments led, respectively, to the following conclusions: (1) A reduction in stress during adaptation to supine restraint permits or promotes grooming and either independently facilitates penile erections and flips or, possibly, the grooming itself further relaxes the male, permitting the expression of sexual reflexes; (2) It is primarily paw grooming that is caused by, and perhaps enhances, the developing adaptation to restraint, whereas genital grooming is precipitated in particular by the occurrence of penile reflex clusters; (3) The cutaneous stimulation received by the penis during copulation may not be a significant factor in regulating the probability or duration of genital grooming; (4) Changes in the penis or in neural activity associated with penile erections are more likely to lead to genital grooming than vice versa. It follows that pharmacological and other physiological treatments may affect the incidence of genital reflexes and grooming by influencing part of a chain of events of by affecting a process (e.g., “stress” or adaptation to stress) that in turn can affect the incidence of both sexual reflexes and grooming.