Successive introductions of new females can maintain this behavior.
Species with approximately equal numbers of reproductively active males and females less likely to have
this, but more common a single male group.
If a male rat is castrated (testes removed), his sexual activity eventually ceases.
Behavior can be reinstated by injections of testosterone.
Sexual behavior of male rodents depends on testosterone.
Injections of testosterone increase weight of seminal vesicles in castrated rats.
Testosterone:
neural basis of this activational effect.
Hormonal Control of Sexual Behavior
Oxytocin
secreted by
posterior pituitary gland
Oxytocin -- contraction of the smooth muscle of the milk ducts, the uterus, and the male ejaculatory
system
Oxytocin -- also serves as a neurotransmitter in the brain.
It is also produced in males, where it plays no role in lactation.
Hormonal Control of Sexual Behavior
Oxytocin is released at the time of orgasm in both males and females and appears to contribute to the
contractions of the smooth muscle in the male ejaculatory system and of the vagina and uterus.
Oxytocin – also involved in pair bonding.
Hormonal Control of Sexual Behavior
Prolactin
is also involved in male sexual behavior.
Prolactin is released by anterior pituitary and stimulates milk production in females.
In males it contributes to refractory state.
Hormonal Control of Sexual Behavior
Hyperprolactinemia:
excess prolactin
This hypersecretion can be due to a prolactin-secreting tumor,
pregnancy, or the use of numerous
medication
Men – hallmark symptom – loss of libido
Side Effects of Psychotropic Medications
Many psychotropic medications including SSRI’s have side effects including reduced libido and sexual
dysfunction.
Recent study found chronic use of painkillers also displays this effect
increased prolactin
Hormonal Control of Sexual Behavior
In some rodent species,, females adopt a posture that exposes her genitals to the male during estrus
--
receptive period in the estrous cycle.
Lordosis:
spinal sexual reflex: arching of the back in response to approach of a male or to touching the
flanks, which elevates the hindquarters.
Hormonal Control of Sexual Behavior
