Sensory control of the male rat's copulatory thrusting patterns

Behavioral Neuroscience, 1999

Physical contact is not necessary for male rats to display penile erection when placed in the vicinity of females in estms (noncontact erection, NCE). The modality and reception of sensory stimuli for the induction of NCE were analyzed. Olfactory bulbectomy eliminated NCE, and destruction of olfactory mucosa by zinc sulfate solution caused a significant suppression of NCE, whereas removal of the vomeronasal organ had no effect. Fresh urine collected from estrous females, but not fresh feces, induced NCE. Neither devocalization of estrous females by cutting the inferior laryngeal nerve nor deprivation of visual cues by placing an opaque barrier between the subjects and stimulus females disrupted NCE. The results indicate that olfactory cues emitted by estrous females induce NCE via the olfactory epithelium. Contrary to what had been suggested by previous experiments, vomeronasal inputs are not indispensable for the induction of NCE. Male rats display penile erection in several different contexts, for example, during copulation, in response to the retraction of the penile sheath (reflexive erection; Hart, 1968), and during paradoxical sleep (Schmidt, Valetta, Schmidt, Wackier, & Joust, 1994). A recent addition to the list of behavioral contexts for the display of erection is in response to inaccessible estrous females (Sachs, Akasofu, Citron, Daniels, & Natoli, 1994). Because physical contact is not required, Sachs et al. (1994) termed the phenomenon noncontact erection (NCE). It is obvious that dissimilar central nervous system mechanisms operate to induce penile erection in different situations. Medial amygdala lesions abolish NCE but not reflexive erection (Kondo, Sachs, & Sakuma, 1997). Lesions of the medial preoptic area impair copulatory behavior but have little or no effect on NCE (Liu, Salamone, & Sachs, 1997). Destruction of the raphe obscurus disrupts copulatory behavior but enhances NCE (Kondo, Yamanouchi, & Sakuma, 1996). Serotonergic depletion by systemic p-chlorophenylalanine induces NCE in Wistar rats (Matsu

Physiology & Behavior, 1982

Journal of Urology, 1989

A model has been developed for the study of penile erection in the Sprague-Dawley rat. Anatomical dissections demonstrate a bilateral ganglion lateral to the prostate called the major pelvic ganglion. This ganglion receives input from the pelvic and hypogastric nerves and innervates the pelvic viscera. A large fiber from the major pelvic ganglion courses along the urethra and innervates the corpus cavernosum, the cavernous nerve. In 40 animals, electrical stimulation of either the cavernous nerve or the pelvic nerve resulted in reproducible repetitive tumescence of the corpora cavernosum. Following ablation of the cavernous nerve, electrical stimulation failed to produce erections. Standard mating behavior tests of mounting, intromission and ejaculation in 38 rats showed that surgical ablation of the cavernous nerve resulted in a decrease in the rate of intromissions and ejaculations compared with sham operated controls. Present models for the study of erection have been limited to the dog, monkey and cat. The rat model presented here offers several advantages over these existing models: 1) the cavernous nerve is easily identified, 2) electrical stimulation is easily accomplished and reproducible, 3) behavioral and neurophysiological studies are possible, and 4) animal purchase, housing, and maintenance costs are low. These advantages make this model a uniquely useful tool in the further study of penile erection.

Journal of Comparative and Physiological Psychology, 1966

6 sexually experienced male rats of the Si strain copulated under 2 experimental and 2 control conditions. Experimental conditions consisted of placing lidocaine anesthetic on the male's penis either just before exposure to a female or during his first postejaculatory interval. Control conditions consisted of comparable applications of Vaseline. Anesthetic conditions resulted in incapacity to achieve intromission for an average of more than 20 min.; during this time males continued to mount females with relatively high frequencies. The effect is interpreted in terms of the 2-component nature of the intromission response; partial sensory deprivation affects capacity for sexual performance while leaving sexual arousal intact.

Physiology & Behavior, 1994

Participation of pelvic nerve branches in male rat copulatory behavior. PHYSIOL BEHAV 55(2) 241-246, 1994.--The role of the pelvic nerve branches in the mediation of copulatory behavior was investigated. The somatomotor or the viscerocutaneous branch of the pelvic nerve was bilaterally sectioned in sexually experienced male rats. Somatomotor branch surgery had no detectable effect. Viscerocutaneous branch transection altered copulatory parameters that reflect impairments in penile erection and seminal plug emission. The altered behavioral parameters approached or reached presurgical and sham values 21 days after transection, indicating that the damage to erectile and ejaculatory function was transient. It is suggested that animals with viscerocutaneous branch transection recover copulatory etficiency through a compensatory plastic mechanism, possibly involving the hypogastric nerve.

Behavioural Processes, 2021

The assessment of sexual behavior in male rats with the aim of unraveling underlying neurobiological mechanisms has in the recent decades been reduced to the annotation of mounts, intromissions and ejaculations. To provide a better understanding of the structure and patterns of copulation, it is necessary to extend and tailor the analysis to the natural organization of male rat copulation. This will lead to better formulation of hypotheses about neurobiological underpinnings of behavior. Mounts and intromissions are naturally organized in mount bouts consisting of one or more copulatory behaviors and are interspersed with time outs. We hypothesized that time outs and the post-ejaculatory interval (inter-copulatory intervals) are related and possibly under the control of a common copulatory inhibition mechanism that is the result of penile sensory stimulation. To test this hypothesis, we analyzed sexual behavior in male rats of three different cohorts from three different laboratories. Results showed that the post-ejaculatory interval and mean time out duration are strongly correlated in all cohorts analyzed. In addition, we showed that individual time out duration is at least partially predicted by the sum of sensory stimulation of copulatory components in the preceding mount bout, with more penile stimulation associated with longer time outs. These findings suggest that both time out and post-ejaculatory interval duration may be determined by the magnitude of sensory stimulation, which inhibits copulation. Whether the same neural pathways are involved in the central orchestration of both time outs and the postejaculatory interval should be subject to future studies.

Journal of Urology, 1993

An animal model using the spinal rat was characterized. Electrical stimulation of the dorsal nerve of the penis elicited reflex tonic erections of the penile body and reflex bulbospongiosus muscle activity, flips and ejaculations. The tonic erections of the penile body are independent from contractions of the bulbospongiosus muscle and appear to be the result of a neurovascular process. Our observations suggest that reflex bulbospongiosus muscle activity, flips and ejaculations are a single complex reflex response, which we define as reflex ejaculatory response. Two parameters predicted the occurrence and type of reflex response. The visualization of bulbospongiosus muscle activity during surgical isolation of the dorsal nerve of the penis was sufficient to anticipate the elicitability of reflex ejaculatory responses. The latter, together with a systemic systolic pressure 2: 73 mmHg., warranted the elicitability of reflex tonic erections. The similarities found in the physiology of rat tonic penile body erections and of human erections make this model promising for further elucidation of sexual function. Moreover, the present model may prove useful for the investigation of neurogenic erectile dysfunction, and of neurogenic ejaculatory disorders.

Urologia Internationalis, 2001

Electromyogram (EMG) recordings were made from the bulbospongiosus (BS) and ischiocavernosus (IC) muscles of the awake male rat in order to evaluate the roles played by these muscles in the implementation of penile intromission during a copulatory encounter. Male rats with bipolar wire electrodes implanted chronically in the BS and IC muscles were mated with sexually receptive females. Concurrent videotape recordings established a relationship between EMG and components of male rat copulatory behavior, i.e. mount, intromission and ejaculation. On EMGs recorded from the IC muscle, the initial low-amplitude phase at the initiation of each behavioral component was distinguished from the late high-amplitude phase whenever the male accomplished mounting or intromission. In the BS muscle, the late high-amplitude phase was observed only when the male accomplished intromission. Power spectrum analysis by fast Fourier transformation revealed that in the IC muscle the two phases differed at an overall range of 100-1,000 Hz. In the BS muscle, however, the spectra of the two phases differed at a specific range of 400-600 Hz. Recruitment of additional motor units would culminate in such a characteristic rise in the power spectrum. The results suggest that somatosensory inputs contingent on the intromission cause such recruitment in the BS to regulate penile cups and other movements.

Physiology & Behavior, 1995

BERNABI~, J., O. RAMPIN, F. GIULIANO AND G. BENOIT. lntracavernous pressure changes during reflexive penile erections in the rat. PHYSIOL BEHAV 57(5) 837-841, 1995.-Reflexogenic penile erections have been previously described in the rat. However, exact involvement of the corpus cavernosum in reflex responses is indefinite. We report changes in intracavemous pressure (ICP) recorded in 10 awake rats by means of a telemetric device. The ICP changes and penile reflex responses (lengthening of the penile body, glans erection, cup, and flip) were recorded during ex copula tests. Each type of penile response was characterized by a specific ICP variation. Mean maximal ICP increase during lengthening of the penile body was 58.6 mmHg, during glans erection 67.3 mmHg, during cups 99.1 mmHg, and 215.2 mmHg during flips. ICP increases to 35.1 mmHg immediately preceding each cluster of penile responses. This study provides quantitative data on the involvement of the corpus cavernosum during reflexive ,erections. Tumescence of the corpus cavernosum was present during glans erection and suprasystolic ICP peaks occurred during flips. ICP measurements during reflexive erections should bring new insights into the analysis of their physiological mediation. Corpus cavernosum Telemetry Penile reflex Rat

Physiology & Behavior, 1976

DAHLOF, L.-G. AND K. LARSSON. lnteractional effects of pudendal nerve section and social restriction on male rat sexual behavior. PHYSIOL. BEHAV. 16(6) 757-762, 1976. -Transection of the pudendal nerve causing desensitization of the glans penis impaired the sexual behavior of male rats. Compared to intact males, fewer animals performed intromissions and ejaculations while no decrease in mounting frequency was observed. The total sexual activity as measured by number of mounts and intromissions was decreased and the copulatory efficiency as measured by the ratio of intromissions and total sexual activity was lowered. The impairment of the sexual activity following penile desensitization was more marked in inexperienced rats than in experienced ones. It was concluded that penile stimulation, although not a prerequisite for any specific component of the mating pattern, still is necessary for maintaining the behavior at a normal performance level.