Estrus hypothalmus returns to negative feedback by e

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Estrus: Hypothalmus returns to negative feedback by E & P. Corpus luteum grows giving rise to increases in progresterone. Notes: Estrous (behavior) = proestrus (endocrine) phase Similar (perhaps identical) hormonal regulation in menstrual and estrus cycles
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Measuring Estrous Cycle in Rodents
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Neuroendocrine control of ovarian steriods.
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+/- Unknown mechanisms switch hypothalamic response to estrogen from negative to positive feedback.
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Figure 6.24 The ovarian cycle in rats
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E alone can induce a lordosis response that is dose dependent but there is an even better response to E & P together Effects of Ovarectomy (OVX) on F sexual behavior in rodents
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Progesterone Antagonists Reduce both Proceptive & Receptive Behavior RU 486 is a P receptor antagonist It dose dependently decreases Lordosis scores and Proceptive behaviors (ear wiggles and hop darts)
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Figure 6.17 Estradiol enhances proceptivity in the absence of male interest
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Female Rat Pacing of Copulation Females control rate of copulation at slower rate than males; Pacing ”. Females show a PEI that leads to termination of receptivity Females also show Coolidge effect Female PEI
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Male Rat Sexual Reward: Conditioned Place Preference Males will spend more time in context paired with ejaculation. Equals “good place” pulate to ejaculation No Copulation
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Importance of Female Rat Pacing Pacing is critical for sexual reward in females (and males) e.g. conditioned place preference Martinez & Paredes Hormones and Behavior 40, 510–517 (2001) F Pacing increases the likelihood of pregnancy
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Female:Female competition Females compete for male that is mating. Notice female 1 (dominant) takes relatively fewer intromissions but all of dominant male’s ejaculation. Her dominance is expressed by first choice of males to sire her offspring.
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Sex and the Brain Males Medial nucleus of amygdala receives important sensory information and sends info to the MPA large olfactory component Lesions reduce sexual behavior Medial preoptic area of the hypothalamus (MPA) is essential for sexual behavior lesions—no sex Specialized region Sexually Dimorphic Nuclei (SDN) Glutamate measured during sexual behavior Receives input from medial amygdala, BNST, & CeTA MPA is connected to the ejaculation generator via the PAG then to the nPGi in the medulla Ejaculation can happen at the level of the spinal cord Neurons that control it are called Lumbar spinothalamic (Lst) cells—called ejaculation generator
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Figure 5.17 Regions that are essential to the control of sexual performance in male rats,
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Figure 5.19 Neural pathways in the rat olfactory system
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Brain Areas linked to Behavior Fig. 2. Conceptual model of the dopamine systems that regulate male sexual behavior. Sensory stimuli from a female and from copulation elicit dopamine release in the MPOA and in the mesolimbic and nigrostriatal dopamine systems. MPOA dopamine influences genital responses, appetitive behavior, and somatomotor patterns; mesolimbic dopamine influences appetitive behavior; and nigrostriatal dopamine facilitates the somatomotor patterns of copulation. (From Hull [33], with permission.)
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Figure 5.20 Castration reduces neural responsiveness in the MPOA.
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DA is a Possible Permissive Factor for Male Sexual Behavior Fig. 1. Effects of dopamine on steroid-primed pathways. Inhibitory GABAergic neurons (small
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