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First Year Veterinary School > Reproductive Pharmacotherapeutics - 1 > Flashcards

Reproductive Pharmacotherapeutics - 1 Flashcards

1
Q

Describe the HPG Axis?

A

Hypothalamic–Pituitary–Gonadal (HPG) Axis
Cabergoline, Prolactin, Oxytocin, hCG, eCG, prostaglandins

Hypothalamus releases GnRH , oxytocin (stored in posterior pituitary)–> APG releasesLH + FSH –> Testis releases testosterone, ovary releases estrogen and progesterone.

Red arrows regulates itself.

E.g. you want to increase secretion of progesterone, you can use something that acts like progesterone (exogenous) but you also can give something to stimulate upstream hormone production. If you give a lot more of exogenous progesteorne, eventually it shuts down the system because it stimulates the negative feedback system.

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2
Q
  • Peptides: GnRH, oxytocin
    – Short chains of amino acids. Usually less than 20
  • Protein hormones: LH, FSH, prolactin
    – Longer chains of amino acids.
  • Steroids: estrogens, androgens, progesterone
    – Core of 4 carbon rings
  • Prostaglandins: PGF2α, PGE
    – 20 carbon unsaturated fatty acids
A
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3
Q

GnRH is what type of peptide?

A

Hypothalamic decapeptide

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4
Q

Label the sites in the GnRH peptide pictured.

A

Sites of cleavage = half life –> degraded, metabolized in body. Lot of enzymes in body will cleave peptide –> loses function.

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5
Q

What is the half life of GnRH? How can you lengthen half life?

A

Very short half-life (2–4 minutes).
Give analogue that replaces site of cleavage to make it last longer?

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6
Q

What is the function of GnRH?

A

Stimulating the release of gonadotropins (FSH, LH)
from anterior pituitary/adenohypophysis

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7
Q

What are the clinical uses of GnRH?

A

Clinical Uses:
1. Induction of ovulation or follicular luteinization. Estrogen will positively elicit LH. Need LH surge and then you can tell ovary to release oocyte from follicle.
2. Suppression of gonadotropin secretion (after a
short period of stimulation)

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8
Q

What is the synthesis strategy of synthetic GnRH or long-acting GnRH analogs?

A
  • Synthesis strategy: substitutions in aa positions
    6 and 10
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9
Q

How many GnRH analogues exist? Name them.

A
  • > 2000 analogues have been synthetized!
  • Gonaorelin, buserelin, deslorelin,
    triptorelin, leuprolide
  • Relative potency: GnRH (1), buserelin (20),
    deslorelin (144)

Ferrets: need to shut down entire repro system. Use implant.

Gonna Bus Des Thick Ladies

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10
Q

What type of peptide if Oxytocin?

A

Nonapeptide

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11
Q

Where is oxytocin produced?

A

Synthesized in the hypothalamus and stored in the posterior pituitary

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12
Q

What is the half life of Oxytocin?

A

Short half-life → ~ 7 min (horse)

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13
Q

Describe the action of oxytocin.

A
  1. mediates contractility of the endometrium which has been pre-stimulated with estradiol.
  2. stimulates contractility of the myoepithelial cells that surround mammary alveoli
  3. Presence of oxytocin receptors in the brain (social maternal, bonding behavior)
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14
Q

Describe the clinical uses for oxytocin.

A
  • Uterine evacuation (powerful ecbolic action)
  • Assist vaginal birth
  • Induce parturition in the mare
  • Facilitates milk let-down without having galactopoietic ability
  • Prolong diestrus in mares → estrus suppression

Mare builds up fluid in uterus. Use oxy to evacuate uterus to allow it contract smooth muscle. B/c it contracts, that is why it can also assist with birth as well.
In vaginal birth, using oxy can be dangerous if not used properly. If uterus continues to contract, it will rupture.
Oxy is more reliable to induce in mare.
Stimulates epithelial cells in mammary glands
For secreting prostaglandin ? is the main substance that can cause ? and the pathway itself.

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15
Q

List the drugs that act like oxytocin.

A
  1. Mesotocin
    * a functional homologue to oxytocin in birds and other invertebrates as well that do not use oxytocin.
  2. Carbetocin
    * Synthetic oxytocin analogue
    * Half-life in horses: ~ 17 min. Not approved to be used in the U.S.
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16
Q

Describe the structure of gonadotropins.

A

Two subunits: α and β subunits

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17
Q

List the Pituitary gonadotropins.

A

luteinizing hormone (LH), follicle-stimulating hormone (FSH)

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18
Q

List the Nonpituitary gonadotropins

A

: human chorionic gonadotropin (hCG) and equine chorionic gonadotropin (eCG)/pregnant mare’s serum gonadotropin (PMSG)

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19
Q
  • hCG: LH-like > FSH-like
  • eCG: FSH-like > LH-like (when in own species) (In equids, eCG binds primary to the LH receptor)
A

if a lot of ECG secreted during pregnancy. if there are a lot of follicles, what is the consequence ? stimulates ovulation or lutenization of folliucles… secerete more progesterone.

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20
Q

Describe the action of gonadotropins.

A
  • Action:
  • Promote folliculogenesis, spermatogenesis and steroidogenesis
  • Induce ovulation (LH, hCG)
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21
Q

Describe the clinical use of gonadotropins.

A
  • Clinical Use:
  • Estrus induction (referring more to FSH)
  • Luteinization of follicular cysts (more LH –> lutenization of cysts)
  • Ovulation induction
  • Challenge testing to diagnose the presence of testicular/ovarian parenchyma (ovarian remnant syndrome; how cna you detect? tissue itself may not secrete much sex hormone but if i give more LH or ecg it will stimulate seceretion. Use stimulation test to confirm your suspicions).
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22
Q
A

Beta subunit –> difference

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23
Q

Describe the structure of prolactin.

A

Prolactin: 198-amino acid glycoprotein synthesized by the lactotrophs of the
adenohypophysis

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24
Q

How does prolactin work in the body?

A

Hypothalamic dopamine has inhibitory control over prolactin secretion at the
pituitary level: act on D2-dopamine receptors of the lactotrophic cells
* Dopamine agonists inhibit prolactin secretion: e.g. bromocriptine (older drug),
cabergoline (usually use), pergolide
* Dopamine antagonists increase prolactin secretion: e.g. metoclopramide,
phenothiazines, domperidone, sulpiride

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25
Q

How does serotonin function in relation to dopamine?

A

Serotonin inhibits dopamine secretion at the hypothalamus and therefore
indirectly stimulates prolactin secretion: e.g. metergoline

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26
Q

Describe the clinical use of dopamine agonists.

A

Dopamine agonists (↓Prolactin)
* Induce luteolysis (lysis of corpus luteum) during
second half of pregnancy in dogs
* Prolactin is one of two luteotrophs in the dog
(along with LH)

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27
Q

Describe the clinical use of dopamine antagonists.

A

Dopamine antagonists (↑Prolactin)
* Stimulate mammary gland development
(e.g. Fescue toxicosis in mares) Remove mare from pasture, remove toxin, and then give domperidone which is a dopamine antagonist.
* Induction of cyclicity in deep anestrous mares

28
Q

Steroids are synthesized from?

A

Cholesterol
If animal is very lean, and not much cholesterol, will not secrete many steroids.

29
Q

How do steroids enter the cell?

A

Circulating steroids bind to and penetrate cell membranes of
target cells and then bind to intracytoplasmic receptors, inducing
nuclear production of mRNA, which codes for new protein
synthesis by the target cell

30
Q

What is the common molecular core of steroids?

A

cyclopentanoperhydroperhydrophenanthrene

31
Q

How many carbon rings do steroids have?

A

Four carbon rings A,B,C and D

32
Q

Progesterone and progrestins mimic?

A

Both mimic the effects of the corpus luteum (CL).

33
Q
  • Progesterone is produced by the ?
  • Progestins are ?
  • Medroxyprogesterone acetate (MPA), Megestrol acetate (MA),
    delmadinone, altrenogest
A

CL
synthetic analogs

34
Q

Describe progestin behavior once administered. What happens when progestin therapy ceases?

A
  • Progestins act on progesterone receptors in the hypothalamus/pituitary,
    increasing the negative feedback and decreasing FSH and LH output
  • The withdrawal of progestin therapy initiates a new estrous cycle and
    ovulation.
35
Q

Describe the clinical applications of progesterone and progestin.

A

Clinical applications:
* Support pregnancy
* Estrus suppression
* Suppression of libido in male dogs
* Treatment of prostatic hyperplasia in dogs.

36
Q

Name the two drugs that act like antiprogestins.

A

Aglepristone (RU 534) and mifepristone (RU 486)

37
Q

Are antiprogestins used in the U.S.?

A

No, but you can request.
Requires special documentation from FDA (import from foreign country)

38
Q

Describe the function of antiprogestins.

A

Act as true receptor antagonists: preventing the uterine effects of progesterone
without initially decreasing serum progesterone concentrations

39
Q

List the clinical applications of antiprogestins.

A
  • Pregnancy termination in bitches and queens
  • Medical treatment of pyometra
  • Induction of parturition
  • Planning of an elective cesarean section
  • Treatment of feline mammary fibroadenomatosis (too sensitibe to progrsterone resulting in this condition, so use antiprogestins).
  • Treatment of hypersomatotropism (acromegaly) (progesterone will increase growth hormone which incentivizes insulin?).
40
Q

List the forms of testosterone. What are their clinical applications.

A
  • Testosterone cypionate, testosterone propionate and
    testosterone ethanate: synthetic esters of testosterone
  • No clinical use in animal reproduction
41
Q

What is Mibolerone? What is its function?

A
  • Mibolerone: synthetic, androgenic, anabolic steroid (testosterone)
  • blocks the release of LH from the anterior pituitary by negative feedback
  • labeled in the USA for estrus prevention in bitches
42
Q

What is finasteride? What is its function? Clinical applications?

A
  • Finasteride is an antiandrogenic drug.
  • Inhibits 5α-reductase, an enzyme responsible for the metabolism of
    testosterone to dihydrotestosterone in the prostate
  • Clinical applications: used for treatment of prostatic diseases in dogs,
    including canine benign prostatic hyperplasia (BPH)
43
Q

What is osaterone acetate (Yzopane)? What is its function? Clinical applications?

A
  • Osaterone acetate (Ypozane) is an antiandrogenic drug
  • Chemically related to progesterone, and as such it has anti-androgen and
    progestagen activity
  • Treatment of BPH (not available in the USA)
44
Q

Estradiol and derivatives
* 17β-Estradiol; estradiol benzoate, cypionate and valerate (estradiol esters);
diethylstilbestrol and zeranol (nonsteroidal estrogens); estriol (derivative);
tamoxifen, clomifene (anti-estrogen/partial agonist effect)

A
45
Q

Describe the action of estradiol and derivates.

A
  • Action:
  • Stimulate sexual behaiour and maintain the reproductive tract during estrus
  • Cause proliferation and cornification of the vaginal epithelium, endometrial
    proliferation and increased uterine tone
  • Negative feedback effect on pituitary gonadotropin secretion
  • Affect oocyte transport in the oviduct as well as local oviductal conditions
  • Outside the reproductive tract: calcium deposition, accelerated epiphyseal
    closure, anabolism
  • Toxicity can cause bone marrow aplasia!
46
Q

What are the clinical applications of estradiol and derivates?

A
  • Clinical applications:
  • Estrus induction (diethylstilbestrol in dogs)
  • Mismating in dogs (not recommend)
  • Treatment of vaginitis in prepubertal or spayed bitches
  • Treat urinary incontinence after spaying in the bitch (Estriol)
  • Estrus synchronization (via negative feedback in HPG axis)
  • Not for food animals in USA
47
Q

Dexamethasone is what type of agent? What is its function?

A
  • Abortifacient agent
  • Enhancing the maturation of fetal lungs: just before parturition or before a
    cesarean section
48
Q

When were Prostaglandins (PGs) first discovered?

A
  • First discovered in seminal plasma; thus believed to be from the prostate
    *
49
Q

What is the biochemical classification of PGs?

A

Biochemical classification: eicosanoids, 20-carbon unsaturated fatty acids

50
Q

How are PGs synthesized?

A
  • PGs are synthesized from available arachidonic acid derived from cell membrane phospholipids
51
Q

What are the important PGs in reproduction?

A
  • Important PGs in reproduction: PGE (1 and 2) and PGF2α
52
Q

What is the natural analog of Prostaglandin F2α and derivates? Synthetic analog?

A
  • Natural analog: Dinoprost tromethamine (salt)
  • Synthetic analogue: Cloprostenol
53
Q

Why are animals sensitive to PGF2α?

A

force contraction of SM so we suggest that you do not give IV.
* Highly-sensitive: DO NOT administer PGF2α intravenously

54
Q

In farm animal species, PGF2α is synthesized in ?

A
  • In farm animal species, PGF2α is synthesized in the uterine endometrium and released
    in late diestrus and at parturition, causing luteolyis (CL regression)
55
Q

What is the action of PGF2α?

A

Action:
* Luteolytic
* Causes contraction of smooth muscle

56
Q

What are the clinical uses of PGF2α?

A

Clinical Use:
* Induce luteolysis/abortion, control estrous cycle
* Ecbolic (oxy + PGF2a have been used in combo to evacuate the fluid from the uterus)
* Treatment of pyometra (these drugs can cause luteolysis and contraction SM in uterus helps it evacuate the pus)
* Facilitate semen collection (contraction of smooth muscle e.g in vas deferens and epididymys which are storage sites for sperm).

57
Q

PGE 1 is?

A

Misoprostol

58
Q

PGE 2 is?

A

dinoprostone

59
Q

PGE 1 and 2 can both work inthe?

A

Male and female repro tract

60
Q

PGE 1 and 2 actions

A

Action: vasodilation, relaxation
* Male target tissue: penile tissues (erection)
* Female target tissue: mature follicles, smooth muscle of uterine tubes, uterus
and cervix

61
Q

Clinical relevance of PGE 1 and 2?

A

Clinical relevance
* Cervical ripening (seen in sheep or goats upon parturition - relaxes cervical muscles to help with dilation), myometrial contractions, elective abortion
* Tubal (oviductal) obstruction
* Unfertilized oocytes become retained in the uterine tubes of mares and
may form “oviductal masses” that may cause obstruction and infertility

62
Q

What are the clinical uses of Melatonin?

A
  • Clinical uses:
  • Induce/suppress the estrous cycles depending on type of seasonal breeders
  • Treatment of atypical alopecia in dogs (Alopecia X)
  • Oral, implant: most products are not FDA-approved
63
Q
  1. What would be the drug of choice for promoting follicle development?

Question 1 options:

A. FSH

B. LH

C. hCG

D. Progesterone

A

A

64
Q
  1. What kind of drug can you use to induce a mare with a pre-ovulatory follicle to ovulate?

Question 2 options:

A. FSH

B. Progesterone

C. Oxytocin

D. GnRH analog

A

D

65
Q
  1. What is the reproductive effect of prostaglandin F2alpha on mares?

Question 3 options:

A. Induction of ovulation

B. Induce luteolysis on a mature corpus luteum

C. Suppress estrus

D. Prolong the life span of a mature corpus luteum

A

B

First Year Veterinary School (43 decks)

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