Induced ovulators

Question 1

Spontaneous Ovulators

Answer 1

Ovulation is brought about totally in response to hormonal changes (no stimulation needed)

Question 2

Induced ovulators

Answer 2

Requires stimulation of the vagina and/or cervix for ovulation to occur

**GnRH causes them to go into heat, BUT it does not cause ovulation.

Question 3

LH surge inducing ovulation

Answer 3

-both in spontaneous and induced ovulaters, the ovulation occurs when a large concentration of LH is released from pituitary (due to surge of GnRH from stimulation) BUT what causes GnRH surge will vary

Question 4

Production of GnRH and Estradiol

Answer 4

-Ovarian follicles produce estradiol which acts on kisspeptin neurons in the hypothalamus
-Results in release of kisspeptin which acts on GnRH neurons (in the 3rd ventricle of the brain) and causes GnRH release
-GnRH causes release of FSH and LH from anterior pituitary

**definitely occurs in spontaneous ovulators, but is also a potential pathway for induced ovulators

Question 5

Relationship between GnRH and LH in pulse secretion

Answer 5

-the frequency of GnRH pulses varies during the estrous cycle
>A spike in GnRH will correlate with spike of LH but will vary during luteal, mid-follicular and preovulatory periods

Question 6

Phylogenetic distribution of mating-induced ovulation

Answer 6

-induced ovulation is present in most mammalian orders OTHER than primates

Question 7

Why is induced ovulation valuable?

Answer 7

1. Good for species that undergo marked population fluctuations Eg. California voles
2. Solitary, nongregarious animals which encounters with other members of the opposite sex is infrequent and unpredictable

Question 8

Behavioural estrus of reflex ovulators

Answer 8

-female must copulate in order to ovulate so female engages in sexual behaviour depending on state of estrus
>some species will display periodic cycles (eg. California voles, ferrets, cats)
>Some species never display behaviour (eg. pine voles, musk shrews) unless they are exposed to conspecific male (pheromonal and tactile stimuli will cause uterine circulating estradiol levels)

Question 9

Categories of exogenous stimuli for inducing ovulators

Answer 9

Category 1

Category 2

Category 3

Question 10

Category 1 exogenous stimuli

Answer 10

-includes species which require minimal copulatory stimulation and when ovulation can be induced rapidly

ex. rabbits, ferret, mink

Question 11

Category 2 exogenous stimuli

Answer 11

Requires at least a single complete copulatory series usually consisting of multiple intromissions followed by ejaculation

ex. raccoons, squirrels, camels

Question 12

Category 3 exogenous stimuli

Answer 12

Require multiple ejaculatory series, occurring either consecutively on the same day or over the course of several days

ex. coles, shrews, cats

Question 13

Patterns of LH release in induced ovulators

Answer 13

There is species variability in the pattern of mating behaviour preceding a preovulatory surge in LH and in the latency, duration, and magnitude of the LH peak after mating

> Ex. Cats duration and magnitude of LH surge is related to the amount of mating stimulation they receive
COMPARED to rabbits where the magnitude of the preovulatory LH surge is independent to the amount of stimulation received

Question 14

Timing of ovulation relative to the onset of mating

Answer 14

Time of ovulation after mating varied greatly between different induced ovulator species

Question 15

Artificial stimulation to cause ovulation

Answer 15

When artificial vaginal-cervical stimulation is used to induce the reflex ovulators, there was lower rates of ovulation and LH release than normal. OR no ovulation occurred

Question 16

Artificial insemination of Camelidae and no stimulation

Answer 16

-LH surge and ovulation with just AI was seen in 75-100% of members

**might mean there is an ovulation inducing factor (OIF)

Question 17

Nerve growth factor (NGF)

Answer 17

A protein found 90yrs ago that plays a role in neuronal survival and is thought to play a role on acting on hypothalamus

Question 18

Nerve growth factor in camelids

Answer 18

Present in abundance in camelid semen

Question 19

Do llamas need NGF or mating for ovulation?

Answer 19

-Believe to need NGF because researchers found that they could induce ovulation by seminal plasma in the absence of copulation

**copulation alone cannot elicit ovulation in the absence of seminal plasma

Question 20

If it is NGF in llamas, then why is estradiol inducing their ovulation?

Answer 20

-It may be because that the endogenous production of ovarian estradiol does not reach the needed threshold to trigger “spontaneous” ovulatory response

**needs seminal NGF to ovulate or estradiol to be given to them that is higher than the threshold

Question 21

Is it NGF or mating in cats?

Answer 21

Experiment: natural mating induced ovulation in all the queens, whereas the cat seminal plasma treatment was effective 67% and the seminal plasma from llamas was effective 17%

Result: there are factors that are present in semen that help with ovulation, but the mechanical stimuli during copulation is critical factor in many induced ovulators

Question 22

Potential ovulatory pathways in mammal species

Answer 22

1. Sensory signal relayed from spinal cord to Kiss resulting in LH surge
2. Estradiol present to help Kiss and result in LH surge
3. NGF have own receptors (TrkA/P75 which can activate further receptors such as Kiss or other that can act on GnRH neurons and cause LH surge