Effect of Age on the Copulatory Behavior of the Male Rat

Hokao, Ryoji; Ito, Tsunekata; Noguchi, Junko; Wakafuji, Yasumasa; Agematsu, Yoshio; Saitô, Tôru; Takahashi, Kazuaki W.; Imamichi, Tomonori

doi:10.1538/expanim1978.41.3_259

Cited by 5 publications

(9 citation statements)

References 9 publications

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“…Previous data regarding patterns of copulatory behavior with age, but not penile reflexes with age have been reported in a few species [2, 4-7, 10, 15]. Hokao et al [4,5] investigated copulatory behavior in WistarImamichi male rats at 10, 27, 44, 67 and 104 weeks of age. The results indicated that the items of copulatory behavior affected in order of age were ejaculation, intromission and mount.…”

Section: Copulatory Behavior With Agementioning

confidence: 99%

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

et al. 2003

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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-

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Section: Copulatory Behavior With Agementioning

confidence: 99%

“…Rates of contact with females, mounting, intromission and ejaculation all decrease in normal old animals [7,10]. 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.…”

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

et al. 2003

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“…In addition, our study shows that PCA caused ejaculation in aged adult rats as well as in young adults. However, aged adult rats paired with receptive females did not ejaculate [2,7] . The question therefore arises, why do aged adults ejaculate when treated with the same dosage of PCA used in young adults?…”

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“…Rates of contact with females, mounting, intromission and ejaculation all decrease in normal old animals [4,5] . In male rats, Saito et al [7] and Hokao et al [2] described that the potency of copulation in aged adults decreased as compared with that in young adults. When yohimbine, an alkaloid found in the bark of Corynanthe yohimbe, was injected intracerebroventricularly in aged adults, they showed higher frequencies of mounting, but not of intromission or ejaculation [7].…”

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Effects of <I>p</I>-Chloroamphetamine (PCA) on Ejaculation in Aged Rats

Saitô

Hokao

Aoki

et al. 1993

Experimental Animals

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“…Libido and copulatory behavior decline in humans and -Note-animals with increasing age [5,8,10,11,18,22]. 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.…”

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

et al. 2009

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As members of Western societies age, sexual function of older (elderly) individuals becomes an important issue, particularly for men. Specifically, copulatory behavior increases circulatory load, which may be related to reports of cardiac sudden death following ejaculation. To further examine this relationship, we compared heart rate (HR) before and after ejaculation in 48-week-old (aged) and 10-week-old (young) male rats. As compared with resting HR, HR after ejaculation was increased by 54.2 ± 3.5 and 41.7 ± 2.7%, respectively, among aged and young male rats. These values were significantly higher than baseline levels (P<0.01). The increases in HR at each time point during copulation were significantly higher in aged male rats than in young male rats (P<0.05 or P<0.01). We also studied decreases in HR following ejaculation and found that aged male rats had a significantly higher HR at 1 and 2 min after ejaculation than young rats (P<0.01). These results suggest that the circulatory load on the aged rat heart is greater than that on a young rat heart during copulatory behavior, especially at ejaculation. In addition, the decrease in HR in aged rats after ejaculation was more gradual than in young male rats. These results suggest that there is a higher risk of sudden cardiac death during sexual behavior in older males.

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Effect of Age on the Copulatory Behavior of the Male Rat

Cited by 5 publications

References 9 publications

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

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

Effects of <I>p</I>-Chloroamphetamine (PCA) on Ejaculation in Aged Rats

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

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