Exam 2 Flashcards
What 2 overlapping phases can male sexual behavior be divided into?
- Appetitive phase: when attempting to gain access to the opposite sex for the purpose of dating
- Consumatory phase: sexual potency, performance, copulatory behavior; shorter than appetitive phase (all androgen-dependent)
evidence for coincidence between onset of sexual interest and puberty
- castration reduces male mating behaviors; disappearing in order
- androgen replacement restores male mating behaviors; reapearring in order
- Sequential ordering of mating behavior suggests that mounting, intromission, and ejaculation have different sensitivities to androgens
Amount of testosterone needed to restore full sexual behavior is …………. if treatment begins after all sexual behavior stops (restoration) than if it begins after castration (maintenance)
greater
Restoration requires ……. doses because androgen receptors ……. without exposure to circulating androgens
higher doses
receptors decrease
Seasonal breeders like hamsters undergo natural………. each year
castration
natural castration
- Testes regression, sex hormones decline, mating stops in the fall (short days)
- Require more testosterone to maintain sexual behaviors
- Even more testosterone is required to initiate sexual behaviors in spring
- If give testosterone immediately after castration need less
how can erections in rats be induced?
- Naturally by electrical stimulation of the cavernous nerve
- by retraction of the penile shaft
evidence for relationship between penile responses and male sexual behavior
Amount of testes to maintain penile reflex and mating behavior is way less than what was originally flowing through the blood
what are the 3 penile reflexes
- Erection and mounts
- Flips and intromissions
- Cups and ejaculations
evidence that entire erectile repertoire programmed in the spinal cord
persists when spinal cord is severed in brain → brain sends inhibitory signals
testosterone metabolites
- Estrogen (estradiol): affects CNS to promote male mating behavior
- DHT: affects neurons in PNS (penile sensitivity) to maintain tactile sensory feedback (positive feedback loop)
POA
critical for integrating environmental, physiological, and psychological information prior to and during mating
POA lesions
- Eliminate sexual performance (male rat mounting behavior) but not sexual motivation- not restored by testosterone
- Disrupt connections to dopaminergic neurons in brain- dopamine treatment transiently activates mating in POA lesioned animals
how do drugs that increase dopamine synthesis affect rats?
increases mating
where are receptors that bind endogenous opioids with rewarding effects?
POA
POA lesion vs stimulation
lesion: disrupt copulation in rats
stimulation: accelerates ejaculation
Optogenetics
can selectively activate specific neurons in a circuit using light
VMH neurons
- more active during aggression and less active during mating
- Need low VMH activity to mate because otherwise will beat up female
FOS activation
chemosensory cues, ejaculation, consummatory behaviors
Neural circuit for male sexual behavior in rodents
- female
- OB
- amygdala
- POA
- midbrain
- brainstem
- spinal cord
- penile erection
3 major integrative dopaminergic systems
- Nigrostriatal tract
- POA
- Mesolimbic tract
integrative dopaminergic systems characteristics
- Regulate motivation, genital responses, and copulation body postures
- All pump dopamine into circuit to turn off the signal coming from the brain
Dopamine
- facilitates sexual behavior by removing tonic inhibition (break in pathway)
- We can measure dopamine levels in POA by microdialysis
- Increases in POA in presence of estrous female
how does castration affect dopamine?
- usually weakens dopamine increase in POA, can be restored with testosterone
- Castration + copulation = still see increase in dopamine in POA
Testosterone increases the probability that dopamine will be released, not essential
hypogonadal/castrated men can copulate ………
normally
Coolidge effect
male rat will mate to satiation with estrous female, but will often immediately resume copulation when presented with new estrous female
Species specific- common in rats. Absent in voles, enormous individual differences in humans
Social environment of mating rodents is artificially simplified in labs
- rats in nature do not mate in pairs
- Rats mated in groups more closely approximates nature: rats can mate at different optimal pace for fulfilling their respective neuroendocrine stimulus requirements
how does presence of female rats affect men rats?
- affects both male sexual motivation and performance
- increases LH and testosterone in males
Involuntary classical conditioning of male sexual behavior widespread
- Male rats spend more time in the side of a cage (in lab) or burrow (in wild) where they previously copulated
- Male rodents unconsciously conditioned themselves- the side of the cage is better because mate more there
Individual differences in male rodent mating behavior
- All given sample dose, all went back to their original levels
- [Androgen] in blood not the cause of sex drive, but different could exist in target tissue sensitivity to estrogens
- Same dose will activate more/less depending on how sensitive the receptors are in that animal
evidence that very low levels of testosterone can maintain normal sexual behavior
- Normal male sexual behavior restored in castrated male rats when given clinically testosterone
- POA testosterone metabolism is similar between sexually active and inactive rats but estrogen receptors reduced
- Low estrogen in males = less sexually active
evidence that bird appetitive and consummatory mating behavior highly dependent on androgens
- Mating behavior disappears immediately after castration
- Resumes after androgen treatment
reasoning for ring doves to convert testosterone into estrogen in the brain
to switch from aggressive courtship behavior to nest-oriented behavior
Japanese quail reproductive behaviors
- Exhibit no reproductive behaviors (do not incubate their eggs)
- Hormonal effects on sexual behavior can be separated from effects on other reproductive behaviors
Japanese quail copulation sequence
(10-15 seconds)
1. Male struts around
2. Male crows
3. Male grabs neck of female and mounts her
4. Male positions cloaca against female’s cloaca
castration and testosterone replacement on Japanese quail
- Castration eliminates all behaviors
- testosterone replacement restores
How do Japanese quail restore quail copulation after castration?
testosterone must be converted to estrogen by aromatase
what does DHT replacement restore in Japanese quail?
strutting and crowing
what can estrogen do in POA?
stimulate dopamine in POA to promote sexual motivation
Golden-collared manakins
- Elaborate courtship behavior- wing snap
- Activated by ANDROGENS, not estrogens
- Reduced by antiandrogens
- Testosterone acts on motor neurons in spinal cord that control wing movements
- Testosterone treatment in juveniles and females will produce wing snap behavior
- Androgen specific effect- testosterone doesn’t get turned into estrogen
what is closely correlated with vaginal cytology?
changes in ovarian function
what stops after ovariectomy?
- Both estrous behavior and cycles of vaginal cytology
- ovaries must produce a cyclic signal that drives these changes
Metestrus/ diestrus
- cornified epithelial cells, leukocytes
- Maturation and development of ovarian follicles
Proestrus
- behavioral estrus (when mating occurs)
- Nucleated epithelial cells
- Maximum follicular development
Vaginal estrus
- Follicles rupture following ovulation, which releases eggs
- Formation of corpora lutea
Cornified epithelial cells
what happens in the cycle if pregnancy does not occur?
corpora lutea degenerates and the estrous cycle continues (no more progesterone?)
what happens in cycle if female becomes pregnant?
- corpora lutea remains large throughout pregnancy (produce progesterone and estrogen)
- estrous cycle is suspended until birth
what stops estrous cycle if succesfully impregnated?
progesterone
what happens with a pseudopregnancy
- if mating is sterile, corpora lutea remain large for 14 days before regressing and estrous cycle is suspended
- hormonally identical to luteal phase in non-pregnant cycle
how long is canine estrous cycle?
7-8 months
canine estrus
- 7-10 days
- Ovulation and mounting occurs, lordosis in females
canine diestrus
- 2-3 months
- Corpora lutea are maintained
canine anestrus
- 4-5 months
- Corpora lutea regress
canine proestrus
- 10 days
- Follicles grow and secrete estrogens
what do dogs do after copulation?
lock together to ensure sperm transmission and fertilization
estrous female dogs characteristics
- exhibit substance mate selectivity
- their urine is attractive chemosensory signal to male dogs
female primate mating behavior
- Male mounts female from behind
- No lordosis- male chimpanzees have enough manual dexterity to compensate for postural differences among females
- Some primates (marmosets) have clearly defined estrous cycles, mating limited to estrus
- Other primates (bonobos, humans) do not limit sexual activity to a particular time
- In female “higher primates”, sexual motivation in relation to fertility is coupled to ovarian hormones, but sexual motivation in relation to social goals is uncoupled
attractivity definition
Stimulus value of female for a particular male, must be inferred by male behavior
Proceptivity
- Extent to which a female initiates copulation
- reflects underlying motivational state (“libido” or “sex drive”)
Receptivity
- state of responsiveness to mating by another individual
- female reactions needed for mating to happen
female monkey experiment attractivity, proceptivity, receptivity
Attractivity- Male mounting rate
Proceptivity- How long it takes to press lever 250 times
Receptivity- Number of ejaculations
- Female monkey trained to press lever 250 times to get access to mate
- Female sexual behavior maximum around time of ovulation (peak estrogen)
Female attractivity
- how attractive the female is TO MALES
- Measured by preference- extent to which a male prefers to be near one female compared to others
- 3-chamber preference test used
- Male rodent spend majority of test period with female to which he is more attracted
what do female morphological changes coincide with?
ovulation (high estrogen)
female baboons in estrus
- experience swelling of the perineum
- Male baboons spend more time looking at and approaching females with swellings
- Male monkeys much more likely to mount ovariectomized females injected with estrogen, but there are enormous individual differences in attractivity (mounting behavior)
Evolutionary perspective- high estrogen = maximal fertility, so females are considered most attractive to males when they are most fertile
Chemosensory cues
that are attractive to males
- female urine and vaginal secretions
- males discriminate estrus from anestrous through these signals processed through vomeronasal organ
Flehmen response
male horses curl back their upper lips to reveal the upper gums to allow female chemosignal to be delivered to VNO
Vomeronasal organ
- Present in humans
- Blocking VNO does not alter ability of humans to detect pheromones → primary olfactory system sufficient for pheromone processing
- Unclear if male humans or higher primates use VNO to select mates
female behavior
- May increase her attractiveness to males
- Females that actively solicit mating have higher “stimulus value” (attractivity) to males
- Male non-human primates spend more time with females that engage in presentation behavior: present their genitalia to males and back up into them
- Almost all contacts prior to mating between male and female non-human primates initiated by females
- Attractivity not solely hormonal: individual preferences across species (female very attractive to one male but unattractive to another)
how can female proceptivity be measured?
by assessing affiliative behaviors: efforts of females to establish and maintain proximity to males
evidence that estrogen enhances proceptivity in absence of male interest
- Nonbreeding season: males not responsive to females
- Ovariectomized, estrogen-supplemented females greatly increase their frequency of sexual initiation
during what phase do women prefer males with masculine traits? and why?
- follicular phase
- Brain activation to masculine faces (high testosterone) changes with menstrual cycle
- Proceptive behavior (seeking males) increased during follicular phase to maximize reproductive success
Behavioral measure
atio between male’s attempt to mate with a female and his success in doing so (“lordosis quotient” in rodents)
evidence that mating posture goes away without estrogen
Mating posture disappears in ovariectomized females of most species
evidence that hormones may not influence receptivity in primate and humans
will mate at all stages of ovarian cycle
Birth control pills may increase or decrease sexual motivation
Hormonal control of receptivity in females can be affected by social factors
- If female monkeys are tested with one male in small area = no relationship between estrogen and receptivity
- When females tested in mixed social groups in large areas = clear relationship between receptivity and estrogen
- Females risk aggression from other females when they solicit males (aversive) → sexual motivation must be high to overcome this aversion
Estrous female rodents do not exhibit mate selectivity in lab settings
- Wild rodents live in demes (breeding units with few adult males, several females, and their offspring)
- Wild rodents mate in groups, pacing of mating behavior under control of female rodent: burrows and runaway systems promote slower mating pace
- Estrous female rodents exhibit mate selectivity in the wild (mate sequentially with several males)
- First and last males to mate sire (are the father of) more offspring than other males
- Females can choose the sires of her offspring
Paced paired mating tests
- female rats are provided with an “escape” area from the male
- Females in paced paired test stay away from male for longer time after intromission than standard mating
Between female rodents in the lab and in the wild, who avoids males after intromission for longer?
wild
how can female rodents discriminate among different types of vaginal stimulation? what disrupts this?
- mount intromission, ejaculation
- perineal anesthesia disrupts
Spontaneous vs induced pseudopregnancy
spontaneous- corpora lutea always follow ovulation
induced- corpora lutea require additional stimulus to develop
rats and mice estrous cycle
4-5
when do rabbits mate?
any time during breeding season
when are Golden-mantled ground squirrels estrous?
only a few hours per year during a single morning
Ovarian cycles in primates and humans
Menstrual cycles
how many follicles develop in primates and humans per cycle?
1
what happens to Corpus luteum after ovulation in primates and rodents?
primates- maintained
rodents- degraded
rodent vs primate estrogen/progesterone peak timing
rodent- estrogen/progesterone peak at about the same time
primate- progesterone peaks later than estrogen
3 types of female reproductive cycles
- spontaneous ovluation and pseudopregnancy (humans, other primates)
- conpulation- induced ovulation, spontanous pseudopregnangcy (cats, ferrets)
- spontaneous ovulation, induced pseudopregnancy (rats, mice, hamster)
what happens in the primate body during menstruation?
- endometrial layer of uterus shed if not pregnant
- Low estrogen and progesterone
follicular phase
- begins at the end of menstruation and ends at ovulation
- LH and FSH released by pituitary stimulates follicular development
- Follicles develop and secret estrogen
- High estrogen positive feedback → LH surge → ovulation
luteal phase
- begins at ovulation, continues until onset of menstruation
- Low estrogen neg feedback → reduced LH and FSH
- Corpora lutea develop and secrete progesterone
how do chemical signals affect rodents?
- from females: suppress ovarian functions
- from males: accelerate puberty, induce estrus, or interrupt pregnancy (induces abrupt release of LH to stimulate follicular growth)
human pheromone expeirment
- conclusion: pheromones may unconsciously affect human menstrual cycle
- pads from follicular phase accelerated LH surge and shortened menstrual cycle of recipient
- pads from ovulation delayed LH surge and lengthened menstrual cycle of recipient
how do receiptive fields respond to estrogen?
expand
4 hypotheses to explain hormonal regulation of neural circuits controlling lordosis
- Trigger hypothesis- brief pulse of estrogen sets off a chain of events that culminates in lordosis
- Maintenance hypothesis- estrogen must be present continually to result in lordosis
- Cascade hypothesis- estrogen “primes” the VMH for subsequent estrogenic facilitation of lordosis; Most supported
- Estrogen must be present at specific, critical times for lordosis to occur
- forebrain- inhbits lordosis
- hypothalamus- POA inhibited by estrogen; VMH activated by estrogen
- midbrain- activated by steroid hormones and peptide signals from hypothalamus
- lower brain stem- integrates info about posture from vestibular system, proprioceptor
- Spinal cord- processes sensory input, products motor output
Precocial offspring
- well developed at birth; require little or no parental care
- Mothers require a greater initial investment (before birth), but lesser post-natal investment
Altricial offspring
- immature, helpless; may or may not display parental care
- Some produce large numbers of offsprings; no parental care
- Fewer offsprings; more parental care
Semi-precocial offsprings
need parental care but can thermoregulate, cling to mother
Maternal aggression
mothers fiercely defend young from intruders, even if previously docile, because maternal behavior triggered by hormonal state (even after C section)
sex differences in parental behavior
males- concentrate effort on mating
Males who pass up additional mating opportunities to help raise their offspring are at an evolutionary disadvantage (unless offspring survival requires parental assistance from 2 adults → Paternal care is relatively rare)
females- concentrate on parental are
Parental behavior in birds
nest building, egg incubation, taking care of hatched young
why is bird parental care common in males?
because males area equally capable as females in providing parental care (compare to mammals, only females lactate)
chicken vs pigeon/dove parental care
chickens- high economic value so lots of interest, but behavior rare among birds in that only mother provides care
pigeons/doves- biparental care; both sexes engage in full parental care and produce crop milk in response to prolactin signals
Types of avian parental care
- Nest parasites (cuckoos)
- Female only (chickens)
- Male-only (malees, jacanas)
- Biparental (>60% of all birds)
Broodiness
- maternal behavior in hens, sitting on eggs in a nest or covering/warming young under wing
- Blood serum from broody hen can induce a non-incubating hen to sit on a nest (due to prolactin)
- After maternal behavior has been initiated by hormones, any kind of touch maintains broodiness (activates circuit)
female bird prolactin
- prolactin increases during egg laying and remain high during incubation
- decline at hatching in birds with precocial offpsring
- declines after hatching in birds with altricial offspring
female bird steroid hormones traits
- Increase with reproductive behavior
- Peak during egg laying
- Decline during incubation
what evokes incubation in female ringdoves?
progesterone and high estrogen → sustained prolactin
how does ovariectomy affect female ringdoves?
eliminates nest building and incubation → restored with estrogen and progesterone injection (not either alone)
how does prolactin affect female ringdoves?
stimulates brooding, crop sac development
how can stress impact maternal care?
elevated coritcosterone decreases prolactin secretion
male ringdoves
- Testosterone not necessary for nest-building, stimuli from female induce males to build nests
- Testosterone necessary for the onset of incubation
- Prolactin required for broodiness, crop milk production
scrub jay alloparents
- (“helpers”, typically older siblings)
- Have higher prolactin levels than non-breeding non-helpers
- Male helpers have lower testosterone and prolactin than fathers
- Female helpers have lower prolactin than mothers but varying estrogen levels
what neural region is associated with avian parental behavior?
POA
* Essential for parental behavior
* Have neurons that produce VIP and increase in activity during nesting
* Prolactin binding to POA receptors much greater in birds that exhibit parental care (TARGET TISSUE SENSITIVITY)
* In males, testosterone reduces paternal care but does not increase prolactin in the POA
Eutherian
mammals that have placenta during pregnancy, widest variety of maternal care
Conditioned place preference
do mothers prefer a chamber previously associated with pups or cocaine?
* Early postpartum: most mothers preferred chamber that had pups
* Late postpartum: most preferred chamber where they received cocaine
* Postpartum day 10: equal preference- motivational state shift?
Parabiosis
- connecting the circulatory system of 2 animals
- Blood of female that just delivered exchanged with that of a nulliparous female
- Nulliparous female exhibited maternal behavior within 1 day: blood-borne factor (hormones)
Oxytocin
rapidly induces maternal behavior in rats (does not cross bbb)
what hormone is activated by parturition?
oxytocin
3 stages of rodent maternal behavior
- Mother-initiated pup contact: mother provides chemosensory cues for pups to attach to nipple
- Mutually-initiated pup contact: contact maintained by tactile stimuli from pups
- Maternal rejection of pups and separation: Rejection due to elevated maternal prolactin and corticosterone = Increased body temp; Pups separate due to loss of attraction to maternal caecotrophs, stimulated by prolactin
mammalian paternal behavior 2 main requirements
- Female unable to rear offspring successfully without male support
- Certainty of paternity must be very high
