diff between lh release in men and women
High frq pulses,
Females also have an acceleration of these pulses followed by large peak ie ovulation
which peptide feeds back to regulate release of lh and fsh
inhibin
what does gnrh facilitate when directly injected
lordosis in females, acts on the brain
what did pfeiffer 1933 find when ovary transplanted into eye capsule
ovulation only in female rats, not males
what did Harris 1950 find
transplanting male pituitary into female host sitll = ovulation
and so the process starts higher than pituitary
what is cycle called in rats
oestrus cycle
hormoanl process leading to lordosis
low estrogen – follicle grows – high estrogen – ovulation – progesterone – lordosis
what happens when ovariectomy + repeated oestrogen for 2 days then progesterone given to rat
female is then receptive
(wihtout ovaries it cant do it if no hormones are injected)
what happens when the same hormonal regime is given to castrated male rates
males do not respond
therefore
the brain is organised differently between males and females
effects of prenatal exposre to sex steroids
when dam expoed to testosterone before they give birth, female offspring = no lordosis after gonadectomy, oestrogen+progestorne
sex steroid effects
not just causes formation of secondary sexual characteristics but also organises the brian
in rats the window of sensitiity is up to 10 days post natal
and brain is sensitive to this long after secondary sexual charac form
product after test+5a-reductase and its effect
5a-dihydrotestosterone
ie DHT
development of external genitalia
product after test+aromatase and its effect
oestradiol
sexual differentiation of the brain
(works only in one way, the reverse reaction is not energetically favourable)
what is gene that codes for aromatase enzyme and where is it expressed a lot
Cyp19a1
cells in hypothalamus express this a lot
which plasma protein binds estrogen
a-fetoprotein (AFP)
afp function in female sexual differentiation
keeps oestrogen from entering the cells (in the brain)
therefore less oestrogen can bind to estrogen receptor and less transc of the genes = feminisation
how does masculanisation of brain happen then
testosterone (unlike oestrogen) CAN enter the brain, converted in cell by aromatase to estrogen - bind to e receptor - gene expression = mascuinisation and defeminisation
what happens when oestrogen injected during pregnancy
the AFP proteins are overloaded with oestrogen, cant bind all of it
so the brain of the female rodents gets masculinised in utero
symptoms of aromatase deficiency in humans
females - pseudohermaphroditism, pubertal abnormalities, cystic ovaries, elevated test, low estrogen (lack of conversion in the ovaries)
males - infertility
freemartinism
Freemartinism is a form of congenital abnormality that results in the infertility of a female calf born as a twin to a male calf
(common blood circulation, ovaries are transformed into sterile testes)
what is first mammalian pheromone identified
androstenone
used to trigger mating beh in pigs
what is 2 sexually dimorphic structures in the vertebrate brain
medial preoptic nucleus
and
sexually dimorphic nucleus of the preoptic area (this is also dimorphic in humans too)
both larger in males than females
sexually dimorphic structure in humans
corpus callosum (more bulbous in females)
what is the actual effect of testosterone after gets into cell (ie what gene does it trigger)
after converted to estrogen
estrogen to e receptor
into nucleus
target gene control apoptosis (so it will either trigger apoptosis or inhibits it)
