Age-related changes in heart rate during copulatory behavior of male rats.

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.

Changes of heart rate during sexual behavior in the female rat.

The authors studied the physiological and behavioral responses during sexual behavior in female rats. For this purpose, electrocardiographs were recoded from conscious and unrestrained females using a radiotelemetry system. Heart rate during sexual behavior rose sharply following the introduction of a sexually active male, displayed a peak level of 425 bpm during male ejaculation, and then rapidly decreased. This pattern of heart rate in females before and after receiving ejaculation was similar to that in males before and after ejaculation. In the rate of decrease in heart rate, however, there was a significant difference between females and males. The present study is the first to show changes of heart rate during sexual behavior in female rats.