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Lecture 12 - March 11

Lecture 12 - March 11 - Hormones and Behavior Mating in...

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Unformatted text preview: Hormones and Behavior March 11, 2010 Mating in Females Rodents only when in behavioral estrus Canines Will only mate when in heat and female actively chooses male Primates Some (e.g., marmosets) only mate during estrus Others (e.g., rhesus, bonobos, humans) capable of mating at any time. rhesus The most effective hormone regimen for inducing estrous behavior in female mammals is the one which most closely mimics the pattern of endogenous hormone secretion. ge ro p ne ro e st ovulation LH estradiol Rats, mice, guinea pigs and hamsters: EB P Estrous Behavior ge ro p e st e on r ovulation LH Estrous Behavior estradiol Rats and hamsters will come into heat if you give them only a large dose of estradiol. ** But they show no proceptive behaviors ** EB Estrous Behavior pr es og t ne ro e ovulation LH Estrous Behavior estradiol So . . . is progesterone really necessary? If you ovariectomize a female rat (hamster, guinea pig) after the peak in estradiol, but before progesterone rises, she won't come into heat. But if you inject her with progesterone, she will. LH e on er st e og pr +P Estrous Behavior estradiol What happens if you give only progesterone? Nothing. Why? Because estrogen priming is necessary to increase neural concentrations of progestin receptors. Effect of estradiol treatment on progestin receptor immunoreactivity (PR-IR) in the ventromedial hypothalamus of ovariectomized mice A: oil vehicle B: EB Female Pacing of Mating In some species pacing of mating is necessary to maintain the corpus luteum ("vaginal code"). Environment, Pheromones, and Reproduction Lee-Boot Effect extended estrous cycle length in group-housed females Whitten Effect acceleration of cycle by male Bruce effect pregnancy interruption Vandenbergh effect puberty delay (female); puberty acceleration (male) Treatment with estradiol alone increases sexual interest in ovariectomized rhesus monkeys Why isn't progesterone required? In female primates there is no sharp rise in circulating progesterone levels during the periovulatory period What determines the likelihood that a woman will engage in sexual relations? There are lots of published reports that the likelihood of sexual activity varies across women's menstrual cycles. The field has been riddled with contradictions. Confounding factors include things like risk of pregnancy and the partner's wishes. Women are more likely to initiate sexual contacts around the time of ovulation. Women are more likely to engage in autosexual behavior during the periovulatory period. If women have sexual contacts with men other than their primary partners, they are more likely to do so during the periovulatory period than at other times in their cycles. Increased risk-taking? Distribution of `double matings' in which women had intercourse with their primary partners and an extrapair partner within 5 days. Neural Basis of Female Sexual Behavior 21 The Lordosis Circuit 22 Lordosis: An Integration of Sensory Stimuli and EstrogenResponsive Neural Circuitry Estrogen necessary to sensitize back to male palpation. Neural circuit sensitive to estrogen at several levels. ER in sensory neurons innervating the flanks Alter threshold for responding ER in POA, AH, VMN, MCG 23 6.22 Receptive fields in the flanks increase in size during estrus Afferent (Sensory System) 25 Circuit is Estrogen Responsive 26 Integration of Hormones, Sensory Input, and Descending Pathways 27 ...
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