Lecture 3.2 Exam 2 Flashcards
(26 cards)
In 1959, William C Young published study on effects of:
perinatal androgen treatment on female reproductive behaviour
females and males of many species typically show:
sexually dimorphic mating postures (lordosis and mounting)
What happens when adult males castrated? Then, treated with androgens?
castrated males will not engage in mounting behaviour, then when treated with androgens will engage in mounting again
William C Young First phase of his experiment:
Injected Testosterone to pregnant guinea pigs throughout gestation period
Some were given larger doses of testosterone than others
pregnant guinea pigs given “higher doses”: some female offspring were hemaphrodites (normal male offspring)
pregnant guinea pigs given lower dose = all “unmodified females” (and normal males
William Young experiment: Second Phase
- In adulthood, all groups gonadectomized
- Then given estrogen+progesterone and paired with stud male.
- Later, injected with androgens and paired with receptive female.
William Young Experiment Results
Compared to controls, androgens given prenatally irrespective of dose (low and high):
In adult females:
* ↓ tendency to exhibit lordosis behavior in response to estrogen/progesterone + stud male.
* ↑ tendency to exhibit mounting behavior in response to testosterone + receptive female
In adult males
* No effect
William Young’s study among others contributed to :
the development of the organization/activational hypothesis
organization / activational hypothesis states that:
This hypothesis states that hormones are involved in the organization of the nervous system: androgens mould in a male like fashion, low levels androgens: nervous system is organized more in a female like fashion
The activation component comes later on as adults: typical males produce androgens + estrogens+ progesterone but more so androgens and that impacts the previously organized nervous system
In females as adults: ovaries produce estrogens + progesterone, those hormones impact nervous system that developed in female like fashion giving rise to behavior like lordosis
Females given androgens prenatally: develop in male like fashion
according to the organization/activational hypothesis (2) :
- Hormones early in development act to differentiate the nervous system
(organizational) - Hormones act on these differentiated circuits later in life to drive behaviors in a
certain sex-typical manner (activational)
In rodents, most behaviors are masculinized by (what and time):
androgen exposure before day 10 of age
no androgen exposure before day 10: will develop in female like fashion
in rodents according to organizational/activational hypothesis masculine behaviours are activated __
in adulthood by androgens
in rodents according to organizational/activation hypothesis feminine behaviours are __
activated in adulthood by estrogens + progesterone
in rodents, androgens are __ for the masculinization of neural sysems
in rodents androgens are NOT responsible for the masculinization of neural systems
testosterone can be converted to DHT via
reductase
testosterone can be converted to estradiol via
aromatase (aromatization)
While fetus is growing in utero mother is producing many hormones of her own (androgens, estrogens, progesterones)
Why are mothers hormones not feminizing male fetus?
Offspring of any sex have proteins made in liver that are ultimately degraded in liver as well that bind to estrogen in the blood: when they bind to estrogen estrogen can not go inside neurons and create change: this “trapping” of estrogen happens in both males and females: mothers hormone can not masculinize growing fetuses system because estrogen captured by proteins**
α and β Estrogen Receptors differently affect sexual behavior in male mice.
* Only __ mice fail to display typical male sexual behaviors.
αβERKO
(knockout of both receptors)
two estrogen receptors: alpha and beta: which typically involved in what
Alpha involved in masculinization
Beta in defeminization
- What hormone(s) masculinize/defeminize the human brain?
In humans its androgens (NOT androgens converted into estrogens)
We know this because Individuals who have mutation in aromatase still show male typical behaviour so its not estradiol
William Young wanted to understand
the behavioral differences in response to hormones (androgens)
Young’s hypothesis:
Perhaps critical period in hormone exposure could underlie the different behavioral patterns observed in adulthood
Neurons that have aromatase inside them can be found in
hypothalamus
estrogen receptors: how many alpha isoforms:
3
estrogen receptors: how many beta isoforms
5
