Developmental Expression of Penile Reflexes and Copulatory Behavior in Male Rats.

Abstract

First, pubertal development of the penile reflexes, e.g., erections, cups and flips in Wistar-Imamichi male rats was investigated following sheath retraction. Second, the penile reflexes and copulatory behavior in the above males were compared between 10 and 44 weeks of age. The penile reflexes in Wistar-Imamichi rats began to appear from day 26, and all males displayed full components of the reflexes on day 47. The occurrence rates and mean numbers of erections, cups and flips in aged adults were significantly low, compared with the young adults. Also, in the observation of copulatory behavior the occurrence rate of ejaculations, and mean numbers of intromissions and ejaculations in aged adults were significantly lower than that in young adults. These results of the present study may suggest that the decrease of copulatory behavior in male rats with age results from the dysfunction of the penile reflexes with age. Key words: Aging, male rats, penile reflexes It is well known that age-dependent changes are prominent in reproductive systems. Normal men experience a gradual decrease not only in sexual activity with age, but also in libido or interest in sexual activity [6]. In spite of the fact that occasional cases of fertility persisting in men in their 90's have been reported, fertility rates decline in men during the normal aging process [2]. Similarly, in normal nonhuman primates and in other mammals such as rats, various measures of male sexual activity decline with aging. Rates of contact with females, mounting, intromission and ejaculation all decrease in normal old animals [7,10]. Kyonan-cho, Japan Saito et al. [15] and Hokao et al. [4,5] demonstrated that conception rates after copulation in aged adult rats decreased compared with young adults.Sachs [14] reported that similar to other mammalian species, male rats display penile erection in several contexts, reflexive erections can be evoked from supine, conscious rats by the tonic stimulation of the retracted penile sheath at the base of the glans penis [9]. The questions addressed here were whether the potency of penile reflex, like the sexual activity, in male rats would decrease with age, and whether a relationship between the potencies of penile reflexes and copulatory behav-

Protective effects of nutritional supplementation with arginine and glutamine on the penis of rats submitted to pelvic radiation

“…We have shown previously that these cells in the rat CC are arranged as a subendothelial layer, whereas in humans they are more homogeneously distributed in the trabeculae (Pinheiro et al, 2000). Furthermore, in the aged rat, when there is already a loss of sexual function (Saito et al, 2003), this smooth muscle layer is markedly thicker and the sinusoidal vascular space is diminished (Machado et al, 2008). Thus, the radiation-induced, transient increase in smooth muscle should likewise lead to a reduction in the lumen of the cavernosal sinusoids.…”

Age-Related Changes in Heart Rate during Copulatory Behavior of Male Rats

“…Saito et al [25,27] demonstrated that penile reflexes and copulatory behavior in 44-week-old male rats are decreased as compared with 10-week-old male rats. Cardiovascular sudden death of elderly men during sexual activity has been reported [19,23,29] and is considered to be a serious problem.…”

“…The aim of the present study was to investigate how ageing influences HR during copulatory behavior in males using a rat model. Experimental animals: On the basis of previous studies and observations [25,27], we used in our experiments specific-pathogen-free male Wistar-Imamichi rats that were 48 weeks old (aged, n=4) and 10 weeks old (young, n=6), and 10-week-old female rats (raised in our laboratory). All animals were acclimatized in an animal room (12-h light/dark cycle and a temperature of 23-25°C) and were given free access to water and food.…”