12. Pharmacology of the drugs influencing sexual function 1. (GnRH and its analogues, gonadotropins, prostaglandins) Flashcards
GnRH. Production. Release. Action.
- Gonadotropic releasing hormone
- Produced by optic and suprachiasmatic areas of hypothalamus (also small amounts in uterus, ovary)
- pulsar and cyclic release (peak release before ovulation)
- stimulates production and release of FSH and LH by pituitary gland (hypophysis)
Uses of GnRH
- to reduce time interval from calving to first ovulation
- to treat ovarian follicular cysts in dairy cows
- to control the time of ovulation at the end of prostaglandin or progesterone synchronisation schedule
- in mares during oestrus -› to maximise the chance of conception and nidation
- to provoke ovulation in rabbits
- to increase fertility rate in sows
- chemical castration, cryptorchidism
Side effects and contraindications of GnRH
- hyperthermia
- allergic reaction
- corpus luteum cysts
- NOT to be used in pregnant animals (embryo death)
- NOT to be used in starved, cahetic animals
What are analogues of GnRH?
Natural GnRH is decapeptide (10 ASS), synthetic are nonapeptides (9 ASS)
- GONADOrelin
- BUSErelin
- FERTIrelin
- DESLOrelin
Application is SC, IM (equine IV), SC implants
What are anterior pituitary gonadotropins?
FSH - follicle stimulating hormone
LH - luteinising hormone
Effects of the FSH:
In the females:
in granulosa cells of the ovaries increases growth of follicle and oestradiol production
In the males:
Increases spermatogenesis in the testicles
Effects of LH:
In the females:
Final maturation of the follicle - oestrogen production, ovulation, luteotropic in most domestic species
In the males:
Increases testosterone production by Leydig cells
Are FSH and LH used in vet practice? What clinical use?
Rarely used because are expensive and have short half-life
In past clinical use was:
LH:
- to induce ovulation
- to leutenize follicular cysts
- to induce follicular growth and ovulation
FSH:
- to induce follicular growth for the purpose of supra-ovulation in cows used for embryo transfer
Non-pituitary gonadotripins. eCG
Equine chorionic gonadotropin
Secreted from endometrial cups of pregnant mares in early pregnancy in order to maintain a luteotrophic (CL stimulation) effect upon the primary and secondary CL in the mare
mainly FSH-like activity and some LH-like activity
Use in females: to induce follicular growth and ovulation (alone or after pre-treatment with progesterone, progestagens), for superovulation
(Increase of litter size, embryo transfer)
In males: to stimulate spermatogenesis and libido
Long half-life: 2-5 days
Non-pituitary gonadotropins. hCG
Human chorionic gonadotropin
Secreted from the chorionic portion of human placenta.
*LH-like activity**
Use in females: to cause ovulation in the mare, for ovarian stimulation, for the treatment of nymphomania (by inducing leteinisation and possibly ovulation)
In males: treatment of cryptorchidism
Half-life: 12-24h
What are non-pituitary gonadotropins?
- eCG - mainly FSH-like activity
- hCG - LH-like activity
Prostaglandins in reproduction
In non-pregnant cycle:
Oestrogen stimulation -› ↑oxytocin receptors -› in late literal phase the binding of oxytocin -› pulsation realise of PGF -› regression of CL
Other effects: activity of smooth muscle in uterus, relaxation of cervix
Use of prostaglandins in reproduction
- oestrus synchronisation
- to induce parturition
- for abortion
- for treatment pyometra, endometritis
What are the prostaglandins analogues influencing sexual function we use? Side effects?
- Dinoprost
- Chlorprostenol
- Etiproston
SE: colic disorders, nausea, vomiting, diarrhoea, bronchoconstriction, abortion
