3. approach to manipulating reproduction ws Flashcards
where does GnRH come from
hypothalamus
how is GnRH produced/controlled
- Pulsatile secretion controlled by tonic centre
- Suppressed by progesterone
- Low oestradiol suppresses GnRH release, while high oestradiol
- stimulates a GnRH surge
what is the taget tissue of GnRH in the female
anterior pituitary gland
what is the source of FSH
anterior pituitary
how is FSH produced/contolled
- GnRH (stimulatory)
- Inhibin / oestradiol (inhibitory)
what is the target tissue of FSH in the female
follicle (granulosa cells)
where does LH come from
anterior pit
how is LH produced/controlled
- GnRH (stimulatory)
- pulsatile release
what is the target tissue of LH in the female
- follicle (theca cells and granulosa in the dominant follicle)
- small luteal cells
where does oestradiol come from
antral follicles
how is oestradiol produced/controlled
- Co-ordinated action of LH on theca to produce androgens and FSH on granulosa to produce oestradiol via aromatase
- As follicle grows E2 increases
what are the target tissue of oestradiol in the female
- uterus
- hypothalamus
- anteriro pit gland
why might we want to manipulate reproduction and/or use reproductive hormones?
- synchronise the herd
- helps for ART and to time so all give birth at similar times
- induce parturition
- abortion
- stimulate ovulation
where does progesterone come from
CL
how is progesterone produced/controlled
LH acting on luteal cells stimulates progesterone production
what is the target tissue of progesterone in the female
- uterus
- hypothalamus
- mammary gland
where does oxytocin come from
- CL
- posterior pit
how is oxytocin produced/controlled
pulsatile secretion of pgf2a
what is the target tissue of oxytocin in the female
- uterus
- mammary gland
where does pgf2a come from
epithelial cells in endometrium
how is pgf2a produced/controlled
oxytocin acting on endometrial oxytocin receptors stimulates pgf2a
what is the target tissue of pgf2a in the female
CL
in which stage of the cycle is this cow. day 30 post mating, no uterine enlargement, no fetal fluids
may be pregnant but probably not, should be able to feel a bit of uterine enlargment (def by day 42), should see fetal fluids by day 28
phase: luteal –> has CL
day 9 of cycle (30-21) ish
what phase of the cycle is this cow in? she is presented as oestrus has not been observed 60 days after calving. uterus has involuted and no sigsn of endometritis
- we expect her to have come into oestrus. should have started cycling around 25 days post calving
- left ovary: small, lots of small follicles
- right ovary: large follicle (maybe too large)
= follicular stage. NO CL
she should be around oestrus now - why not. what can we do to get her back into calf
what are the primary actions of GnRH in the female
stimulates FSH and LH release
what are the primary actions of FSH in the female
- stimulate E2
- stimulates recruitment of small antral follicles
what are the primary actions of LH in the female
- stimulates dominance and growth of large follicles
- stimulates E2 and ovulation
- luteal P4 production
what are some potential pharmacological effects if in follicular phase there is a dominant follicle and no active CL and GnRH is given
- LH surge
- ovulation
wont induce oestrus per say, she might happen to be in oestrus but its primary action is inducing oestrus
what are some potential pharmacological effects if in follicular phase there is a dominant follicle and no active CL and FSH is given
- stimulate to grow and produce oestradiol
- but not going to have any dramatic effect
- can trigger superovulation but not in this case because we have a dominant follicle (needs to have been given in the luteal phase repeatedly when follicle wave is growing)
what are some potential pharmacological effects if in follicular phase there is a dominant follicle and no active CL and LH is given
Ovulation of DF;
Luteinisation of follicular cells
At low doses increase E2.
At high doses switch E2 production off
what are the potential pharmacological effects if an animal is in the luteal phase (dominant CL and follicles at different stages that can include DF) and GnRH is given
- cause LH surge
- stimulate more progesterone production from CL
- ovulate dominant follicle (even though progesterone is supressing ovulation. prog inhibits ovulation through negative feedback on GnRH but we have bypassed and given LH)
- makes accessory CL
what are the potential pharmacological effects if an animal is in the luteal phase (dominant CL and follicles at different stages that can include DF) and FSH is given
depends on where we are in stage of luteal
- can increase dominant follicles if given at end of one wave and beginning of another (must be given when we have a growing follicle, NOT when we alreayd have a dominant follicle
what are the potential pharmacological effects if an animal is in the luteal phase (dominant CL and follicles at different stages that can include DF) and LH is given
- stimulate more progesterone production from CL
- ovulate dominant follicle (even though progesterone is supressing ovulation. prog inhibits ovulation through negative feedback on GnRH but we have bypassed and given LH)
- makes accessory CL
what is the primary action of oestradiol in the female
- Oestrus behaviour
- GnRH release (inhibitory at low concentrations; stimulatory at high)
what is the primary action of progesterone in the female
- Uterus: histotroph
- suppressoestrus
- Suppress GnRH/ovulation
what is the primary action of oxytocin in the female
- pgf2a production if OXTR are present
what is the primary action og pgf2a in the female
regression of the CL
is oestradiol is administered in the follicular phase what happens
- oestrus behaviour
- GnRH/LH surge
- ovulation
if progesterone is administered in the follicular phase what happens
- would enter luteal phase
- inhibit ovulation
- inhibit oestrus
is oxytocin is administered in the follicular phase what happens
no effect
- might stimulate uterine contraction, might help luteolysis along
is pgf2a is administered in the follicular phase what happens
no effect
- will increase regression of CL of already regressing CL
is oestradiol is administered in the luteal phase what happens
- could induce LH surge
- but doesnt really do anything. if high does given will induce luteolysis
is progesterone is administered in the luteal phase what happens
suppression of gonadotrophin and hence follicular maturation
might attenuate luteolysis
is oxytocin is administered in the luteal phase what happens
- no effect really.
- stimulates pgf2a release IF receptors are there (day 15,16,17 of cycle)
- might help along luteolysis. but will only shorten cycle by about a day. not used to manipulate cyclicity
is pgf2a is administered in the luteal phase what happens
- cause regression of CL
- progesterone declines
- enters follicular phase/prooestrus
- come into oestrus within 3-4 days
- doesnt have much effect though on growing or regressing CL
in ruminants and pigs, luteolysis requires hormonal communication between which structures
CL and uterine endometrium
how is luteolysis initiated
how can you induce breeding opportunity in the below scenario
she is in luteal phase
want to induce luteolysis with pgf2a
- AI her as soon as you notice standing oestrus (3-4 days after admin but maybe 4-5 days as says right ovary only has small follicles. need to give time to grow)
- could then inject GnRH 2-3 days later to ensure ovulation happens
- AI her at 2-3 days whether she is displaying signs of oestrus or not
how can you induce breeding opportunity in the below scenario
- she is in follicular phase as DF present
- might be in or about to be in oestrus (increased uterine tone)
- so AI her as will be coming into oestrus tomorrow or day after
- give GnRH/LH to cause LH surge and thus ovulation
