Sexual Behavior

· Reproductive cycle of female mammals is called the estrous cycle (menstrual cycle in primates)
· A female rat in estrous behaves differently which makes the male rat behave differently as well

· The sexual behavior of mammals is linked with ovulation (in primates, females can mate any time during their menstrual cycle)

Pituitary gland and ovaries

A cluster of epithelial cells surrounding an oocyte, which develops into an ovum

A cluster of cell that develops from ovarian follicle after ovulation; secretes estradiol and progesterone-maintains endometrial lining of uterus during later part of menstrual cycle and pregnancy, promotes receptivity in females.

· Sex behavior in male rats depends on testosterone released by testes
o A castrated male rat will cease sexual activity which can be reinstated with an injection of testosterone
· Sexual behavior in female rats depends on estradiol and progesterone released by ovaries
o Ovariectomised rats are not sexually receptive but it can be produced by administering estradiol followed by progesterone

-when receptive; lordosis
-active in initiating copulation. May entice him by sniffing and nuzzling male genitals
-Male rats most responsive to female rat on 'heat'
-males ignore females whose ovaries have been removed, but injections of estradiol and progesterone increase attractiveness

· Intromission, pelvic thrusting, ejaculation, are all characteristics of all male mammals
· When a male rate encounters a receptive female, he will spend more time sniffing, nuzzling and licking her genitals, as well as mount her and engage in pelvic thrusting
· mount several times and intromit on most occations but will ejaculate only after 8-15 intromissions

· If male is exhausted by repeated copulation with the same female, he will respond more quickly if presented with a new female
· Successive introductions with new females keeps performance up for a long period of time

Causes contraction and male ejaculatory sysem

· Androgens are male sex steroid hormones which stimulate development of the male sex hormones
· Androgens have a defeminizing effect; they inhibit the later development of anatomical or behavioral female characteristics

· If a rodent is NOT exposed to androgens at critical time during development (shortly after birth), and treated with estradiol and progesterone as an adult, the rat will engage in female sex behavior
· If a male rat is castrated after birth and given injections of estradiol and progesterone as an adult, it will respond to the presence of another male by assuming lordosis, i.e., acts as if it were female

· If a rodent brain IS exposed to androgens shortly after birth, behavioral defeminization will suppress the neural circuits controlling female sexual behavior and behavioral masculization will allow the rat to engage in male sexual behavior as an adult
· If a female rat is ovariesctomised at birth and then treated with testosterone as an adult, she will attempt to mount and copulate with a receptive female.

· chemicals that carry messages from one animal to another

Groups of female rats when housed together show slowing down of their estrous cycle