-Cyproterone acetate (CPA): antiandrogen and androgen receptor antagonist, -Medroxyprogesterone acetate (MPA): synthetic progesterone and decreases LH and thus T synthesis
What are two components of male sexual behavior?
-Sexual motivation and sexual performance, may be controlled by different hormones
Columbia University obstruction test
...was used to measure sexual motivation
also called potency, consummatory behavior, copulatory behavior
Donald Dewsbury's Copulatory patterns in mammals
16 possible categories, copulatory lock, intra-vaginal thrusting, multiple intromissions, and multiple ejaculations, -Ecological correlates: all rodent species with copulatory locks are nocturnal
Male sexual behavior in rats consists of...
1) Mounting, 2) Intromission, 3) Ejaculation
Intromission in rat copulatory behavior
-5-15 mounts prior to intromission, optimal pattern described as "vaginal code", female rats control pacing of activities
Ejaculation in rat copulatory behavior
sperm plug: substances from prostate, seminal vesicles, coagulating gland, blocks intromission by other males and retains sperm
Rat copulatory behavior (cont.)
-Ultrasonic vocalizations (20-22 KHz), -Post ejaculatory interval: Absolute: no sexual behavior, Relative: sensitive to stimulus value of female
-Resumption of sexual activity in a sexually satiated male with introduction of a novel female, related to stimulus value of female, not present in monogamous rodents like prairie voles
Graham and Desjardin Study (1980)
-Classical conditioning: induction of luteinizing hormone and testosterone secretion in anticipation of sexual activity, -Hypothesis: cues males to learn to associate w/ females during sexual encounters induce hormone secretion
-Behavior begins at threshold T level in (ex. rats), -Behavior varies directly w/ T levels (ex. ferret)
Seasonal patterns in testosterone secretion
-Short-day breeders: Maximum T in Fall (male deer), -Long-day breeders: Maximum T in Spring (male sheep)
Associated & Dissociated Reproductive Patterns (David Crews)
-Associated Pattern: Mating occurs when gonads fully developed and T levels high, present in most species (ex. male deer), -Dissociated pattern: Mating occurs when gonads not developed and T levels low, less common (ex. red-sided garter snakes)
Organizational effects of testosterone
-Timing of perinatal T secretion differs w/ species, -Depends on length of gestation and developmental rate, -T secretion usually occurs before birth in species w/ relatively long gestations
Activation effects of testosterone
1) What hormones are involved? 2) Where do these hormones act?
What hormones are involved?
-T, DHT, and E, -T converted to DHT through 5-alpha-reductase, T converted to E via action of aromtase
-Male sexual behavior activated by conversion of T to E, -Requirements: Aromatase enzyme and estradiol receptor, -Importance: widespread among vertebrates but of little importance in primates, -Testing: Aromatase inhibitors ATD and fadrazole, DHT cannot be converted to E
Where does T or its metabolites act?
-CNS, periphery, or both, -Male rat example: peripheral actions-both T and DHT stimulate penile muscles, - Central actions: Both T and E activate sexual behavior in male rats when implanted into anterior medial preoptic area of hypothalamus, -Penile response latency for peripheral action and intromission latency for central action
-Important in rodents, less so in primates, -Composed of primary and accessory olfactory bulbs plus vomernasal organ (Jacobson's organ)
-Portion of olfactory neuroepithelium located on each side of nasal septum near floor of nasal cavity, -Receptors connect mainly to accessory olfactory bulb via vomernasal nerve, -Accessory olfactory bulb sends input to amygdala and then to medial preoptic area of hypothalamus (MPOAH) via stria terminalis, -Highly developed in rodents, -Absent or regressed in primates and aquatic mammals
-Maylay tapir exhibits flehmen response to the scent of females, -Pulling back the upper lip exposes openings to vomernasal organ
Impairing chemosensory system
-Zinc sulfate to anesthetize nasal epithelium, -Bulbectomy
-Brain area mediating male sexual motivation in mammals, -Receives input from olfactory bulbs >> sends output to medial preoptic area of hypothalamus via stria terminalis, -Neurotoxic lesions disrupt sexual motivation (N-methyl-D-aspartate)
Preoptic area or medial preoptic area
-Required for sexual performance, -Neurons active during copulation as indicated by c-fos activity, Neurotoxic lesions disrupt mating, Electrical stimulation activates mating in T-treated males, -Contains testosterone receptors: T infusions restore copulation in castrated rats, aromatization important as T effects inhibited by ATD or fadrazole
Preoptic area (cont.)
-Sexual motivation persists after POA destruction so males investigate females but never mount them, displacement behavior is drinking -Integrates olfactory and tactile cues critical for copulation (olfactory cues from estrous female, input from vomernasal organ, output to motor neurons of spinal cord mediating copulation), -Castration reduces neural responsiveness in the MPOA
-Dopaminergic output from MPOA required for sexual performance lesions of dopaminergic neurons inhibit copulation
Dopamine agonists (activate copulation)
would be apomorphine and lisuride
Dopamine antagonists (inhibit copulation)
would be haloperidol
Extracellular dopamine in the MPOA
is elevated by cues from females
Excess prolactin PRL in blood...
inhibits male sexual behavior (hyperprolactinemia)
-Generally disrupt male mating behavior, increased endorphins decreases penile erection and copulation, morphine reduces sexual behavior, opiod antagonists such as naloxone enhance sexual behavior, Mu opioid receptors in MPOA mediate rewarding properties of sexual behavior
Erectile dysfunction, nitric oxide (NO), & Viagra
DHT increases NO synthase that increases synthesis of NO, NO increases cGMP that causes penile vasodilation and erection, phosphodiesterase converts cGMP to inactive GMP, and Sildenafil citrate (Viagra inhibits phosphdiesterase)
Reproductive behavior in male birds
-Quail: crowing (DHT mediated, vocalizations controlled by intercollicularis (ICO), ICO contains 5-alpha-reductase, -Mounting: E mediated (via T to E), mounting controlled by medial preoptic area, MPOA contains aromase
whiptai lizards experiment showed that females exhibit "pseudosexual behavior"
What is the hormonal control of pseudosexual behavior?
show female-like behavior and have high E, while postovulatory stage females show male-like behavior and have high progesterone (P)