Chapter 6: Female Sexual Behavior Flashcards
Estrus
Reproductive function in females is cyclic
“Estrus” means “in a frenzy”
In many species, females advertise their reproductive capability and availability during estrus (“heat”)
Strong motivation of female to gain access to males and mate
e.g., willingness to cross electrified grid in rats
Anestrus (not in estrus) will not sustain pain or exert much effort to interact with males
Females are active participants
Estrous Cycle
Estrous cycle: cycle between mating and non-mating conditions in female (4-5 days in rats)
4 stages: diestrus 1, diestrus 2, proestrus (behavioral estrus), estrus
Mating behavior coupled in
time with ovulation
Estrogen and progesterone
- ->ovulation
- ->affect the brain to influence the female’s behavior and induce receptivity
The ovary
Prior to ovulation (diestrus & proestrus):
GnRH from the hypothalamus—> FSH and LH from the pituitary—>
FSH follicles to grow and mature
On the afternoon of proestrus :
Pulses of GnRH become larger and more frequent —>
rapid increase in FSH and LH
FSH—> Theca and granulosa cells of mature.
(Graffian) follicles produce surge in estrogen (“estrus-inducing”) and progesterone
LH from pituitary stimulates ovulation
This is positive feedback
After ovulation (estrus):
Estrogen levels decline
Follicles are converted to corpora lutea which produce large amounts of progesterone (“pro-gestational”)
After ovulation cont’d
Does not mate and not pregnant —> corpora lutea degenerates, P levels drop and the cycle begins anew
Sufficient vaginal stimulation through copulation:
fertile and pregnant —> corpora lutea remain large, estrus cycle suspended
Hormonal Induction of Estrous Behavior:
THEY ARE ALL ACTIVATION
When the ovaries are removed from a female rat through ovariectomy (OVX), estrous behavior disappears
If treated with E alone some, but not all rats dispay estrous behavior
If treated with P alone no estrous behavior
E followed by P normal estrous behavior
Mimics the estrous cycle
In rats, p treatment is 2 dYA AFTER ESTROGEN AND TESTING IN A 4HOUR AFTER PROGESTERONE
ESTRADIOL PRIMES HTE BRAIN TO BE SENSITIVE TO P
Termination of receptivity
P has biphasic effects
AFTER OVULATION, THE LARGE AMOUNTS OF PROGESTERONE SECRETED FROM THE CORPORA LUTEA TERMINATE ESTROUS BEHAVIORAL
Knockout mice
Progesterone receptor knockouts (PRKO)
WHEN OVK, neither wild types nor the PRKO displayed lordosis after treatment with E
P treatment after E estrogen priming induced lordosis in almost all of the wild type mice
Estrogen receptor knockout mice (ERKO)
After OVX:
α estrogen receptor knockout mice (αERKO):
are unreceptive to males even after treatment with estrogen & progesterone
β estrogen receptor knockout mice (βERKO):
Display lordosis to same extent as Wild Type mice
αβ estrogen receptor knockout mice (αβERKO):
like alpha ERKO mice, fail to display lordosis after appropriate hormonal priming
Components of female sexual behavior (Beach, 1976)
Attractivity: stimulus value of a female for a given male
Proceptivity: female initiation of copulation
Receptivity: responsiveness to sexual initiation by the male
All 3 components are at their highest level during behavioral estrus when E levels peak
Attractivity
How attractive the female is to males
Usually measured in terms of preference
Hormones associated with ovulation mediate attractivity in females
E enhances attractivity in OVX females
E-Induced attractivity reduced or abolished by P
Stimulus basis of female attractivity:
Morphological changes that coincide with ovulation
eg, genital swelling in female primates
Chemical cues, e.g. urinary & vaginal secretions
Behaviors, e.g. hopping, darting, ear wiggling in rats; genital presentation in non-human primates
Proceptivity
Appetitive phase
Reflects underlying motivational state
Sexually solicitous behavior that initiates sexual union, but is not copulatory behavior per se
eg, hopping are dating, ear wiggling in rats; solicitous in non-hymn PRIMATES
High concentrations of E facilitate proceptive behavior
IN OVX RHESUS MONKEYS, E INCREASES PROCEPTIVITY IN THE ABSENCE OF MALE….
Receptivity
Consummatory
Those female reactions that are necessary and sufficient for fertile copulation with a male
INDICATED BY A species-specific mating posture IN ALL NONHUMAN PRIMATEs
e.g. lordosis in rodents
Expressed in terms of ratios between a male’s attempts to mate with a female and his success in doing so
Rats: Lordosis Quotient = # lordosis/ # mounts
E is important in receptivity
Receptivity in primates
Female primates are able to copulate at all stages of their ovarian cycles
Suggests that hormones don’t influence female receptivity
But…hormones do play a role in receptivity under certain social conditions
Are females active participants in sexual behavior?
Females have traditionally been assumed to be passive recipients of male sexual attention
Why?
Cultural constraints
Maintaining immobility during lordosis seems passive
Single pair mating tests
Breeding deme
Small breeding units that consist of one or two adult males, several females and their offspring
Females mate with several males simultaneously
Females initiate copulation and control the pacing of mating behavior
How to recreate in lab ?
Female pacing of copulation
When females can pace copulation:
the interval between intromissions is longer (3 min vs 1 min in non-paced mating tests)
they return to the male more slowly following ejaculation
Males learn partner preference
Why is female pacing important?
May be a means of ensuring that she receives an optimal pattern of stimulation (“vaginal code”) for producing offspring
This optimal sensory stimulation induces prolactin release from pituitary, which maintains luteal function and allows for embryo implantation
without it, estrus cycle begins again
