ABSTRACT
The male animal' behaviour helps to stimulate relevant behaviour in the female, while her behaviour stimulates both sexual behaviour and hormonal changes in the male. Sexual behavior of a male rodent depends on the presence of external factors, and of internal factors. Removing the gonads of adult animals completely abolishes the behaviors within days, and the injection of sex-appropriate hormones reinstates them immediately. In animals that have annual breeding cycles, testosterone production almost stops during parts of the year when breeding does not take place. This type of hormone effect is called an activating effect, since the hormone results in the activation of programmed behaviors. The readiness of females of many species to engage in proceptive and receptive behavior depends on cyclic release of gonadal hormones in the estrus cycle. Turning to women, the human menstrual cycle involves a cycle of hormonal changes, including the same sequential secretion of estradiol and progesterone as in rats.
