PHEROMONES AND THE MENSTRUAL/ESTRUS CYCLE

1. PHEROMONES AND THE MENSTRUAL/ESTRUS CYCLE

2. PHEROMONES: ECTO-HORMONES Chemical messengers that are transported outside the body that have the potential to evoke physiological or behavioral changes in another individual of the same species. Types of pheromones: 1. Signalers: cause short term behavioral changes. (mating signal, aggression, lordosis). 2. Primers: cause physiological change at the long run. Affect mainly the HPG axis.

3. While most mammals have VNO in addition to the olfactory organ, humans Lack it.

4. Some groups claim that there is a functional VNO in humans: Vomeropherine (PPD- pregna-4,20-diene-3,6-dione) direct introduction into the VNO had changed FSH/LH pulses pattern in humans. Berliner et al. 1996

5. PHEROMONES ACT MAINELY THROUGH THE VNO-AOB BUT ALSO THROUGH THE MO SYSTEM. IN THE END OF THE ROAD THE HYPOTHALAMUS GETS SIGNALS FROM BOTH ORIGINS.

7. flank marking hamster Mating behavior rat male Singular breeders Marmosets Plural breeder Rodents, humans The male effect ewe

8. Social and reproductive strategies: Plural breeding VS. Singular breeding Marmosets Rats, Humans

9. In some plural groups synchronization of menstrual/estrous cycle have been observed: Rodents: The Lee-Boot effect(Van der Lee & Boot, 1955, Acta Physiol. Pharmacol. Neerl. 4: 442) Grouping several female mice in a cage results in suppression or modification of their estrus cycle (delay of puberty and suppression of estrus; effect is female to female) The Whitten effect(Adv. Reprod. Physiol. 1: 155) involves (1) estrus induction, (2) estrus synchronization, and (3) suppression of estrus in females housed in large group. The induction of synchronized estrus by urinary cues of conspecific male mice in females with group-dependent estrus suppression.

10. Plural Breeders: Humans: The most known phenomenon between females is the : Cycling Synchronization Effect

11. (0-2 days after LH surge) The coupled – oscillator mechanism ‘Ovulatory pheromone’ lengthens cycle, and ‘follicular pheromone’ shortens cycle (Stern & McClintock, 1998).

12. Ovulatory phase pheromones lengthen Follicular stage Follicular phase pheromones shorten Follicular and luteal phases.

13. In rats: All female environment tends to suppress the estrus cycle Induction of spontaneous pseudopregnancy Extension of estrus cycle Prolongation of quiescent period

14. ? However, although the phenomenon are well described, the neuroendocrine correlates of female to female effect in plural breeding group species haven’t been published.

15. Singular breeders: Reproduction is limited to a single female in a group. In this case, a dominant female inhibits the sexual behavior of subordinate Females. Oocytes are arrested in follicular stage. Marmosets- primates with developed VNO- Subordinate female has low LH levels comparing to dominant female. GnRH levels and pulsatility seems to be unchanged.

16. * The effect is not GnRH dependent, what then is the mediator? * Stress is one of the key factors, ACTH and glucocorticoids levels are high in subordinate female. * Opioids, released in response to stress, mediate the suppression of LH in subordinate females. Naloxone prevented the LH decrease. * In another experiment it was shown that subordinate females have demonstrated enhanced sensitivity to the inhibitory influences of E feedback on LH secretion.

17. Proven to be sufficient Cues from dominant female exert 1. increased sensitivity to E negative feedback 2. Inhibition of LH secretion from the pituitary Both lead to hypogonadotropism

18. Male and female pheromonal interaction Humans: • Pheromonal related neuroendocrine changes in human’s brain haven’t been • well studied. • Pheromonal effect on mood and perception in females revealed that • androstenone is perceived as a hedonic scent and that it improves mood • of the recipient female just before and during ovulation, e.g. there is a change • in sensitivity to male pheromone depending on the menstrual stage.

19. Animal model 1. The Whitten effect- Induction and synchronization of estrous (ovulation) among unisexually grouped females in the presence of a male. 2. The Vandenbergh effect- (Vandenbergh, 1969, Endocrinol. 84: 658) Onset of puberty in young female mice can be accelerated by pheromones contained in the urine of adult males . 3. The male effect- enhancement of ovulation during anestrous with the appearance of a male. 4. Female urine causes a rapid induction of LH release and mounting behavior in male.

20. Females mice, exposed to male urine or isolated pheromones, show higher estrous cycle frequency(especially in groups). Jemilio et al. 1986

21. The “Flank marking” behavior of the Hamster • Scent marking behavior. The hamster rubs its flank against • an object to spread pheromones. • Gonadal hormone dependent type of behavior • Used to communicate a variety of social information relevant to reproduction and agonistic behavior. • Males- castration reduces the frequency of flank marking, T restores it. • Females- Frequency correlates with the estrous cycle and levels of E and P during the cycle. (Female mice frequency of urine scent marking is not correlated with changing levels of gonadal hormones).

22. Number of flank marks are more frequent in diestrus2 and proestrus and low in diestrus1 and estrus stages.

23. E replacement to OVX females restores cyclicity of flank marks Progesterone addition inhibits the stimulatory effect of E

24. Flank marking behavior is driven by the activity of arginine- vasopressin in the mPOA AVP injection to the mPOA- and only AVP- induces number of flank marking

25. V1R antagonist inhibits the AVP induction effect.

26. * Female hamsters, implanted with E capsules marked more in response to AVP comparing to untreated females. i.e. Estradiol influences flank marking by altering the sensitivity or responsiveness of the mPOA to AVP. * c-FOS activation studies of flank marking behavior pointed to the BNST, CAN (central amygdala nucleus) and PAG as part of the neural circuitry.

27. Based on observation in rats and mice E induces number of AVP-R (AVP 1aR) (not yet in hamster). Rat mPOA

28. Summary: • Flank marking in the hamster female is a way to pheromonally • inform the conspecific male about her sexual status. • 2. High levels of E, which occur in late diestrus and proestrus, induce • flank marking frequency. • 3. AVP stimulates flank marking frequency by acting in the mPOA. • 4. Possibly, E induces AVPaR1 receptor synthesis in the mPOA and thus • sensitizes the mPOA to AVP.

29. The male effect: similar to Whitten effect but in this case, females are in anestrus. Exposure of female to male or his odor (fleece) out of the breeding season activates LH secretion and synchronization of ovulation. Best known in sheep and goats.

30. The odor signal in ewe is perceived by the MO system rather than the VNO. When chemical anosmia was applied: Considerably less females Responded to male odor. LH pulses frequency, amplitudes and levels were low comparing to control.

31. Further support for the MO tract of the “male effect” was obtained by temporal local inactivation of the Cortical nucleus of the Amygdala or the VMN by Lidocaine.

32. Only inactivation of the cortical nucleus of the Amygdala impaired LH increase in response to male. Gelez & Fabre-Nys, 2004.

33. The role of GnRH in pheromonal sensing: So far, it was shown that sexual related phermone signal results in an increase in LH pulasatility and circulation levels in females. Although not shown here yet, the same phenomenon is observed in males. But, is GnRH involved in this activation? (Recall that GnRH is not involved in the hypogonadotropism of marmoset subordinatefemales)

34. Bedding An attempt to answer whether GnRH mediates LH elevation in male mice when introduced to female odor 90 min 45 min • GnRH expression in the POA • did not increase when exposed • to female odor. (We already now that • LH levels increase). • *However,GnRH was upregulated in • response to an intruder male. • Similar results were obtained with • the syrian hamster (Richardson et al. • GCE, 2004)

35. But mating behavior is induced by ICV injection of LHRH to VNX males. (LHRH is in the circulation and can be transported to many regions in the brain). How does GnRH mediate the detection of female odor and male sexual behavior? Is there another source of GnRH in the brain? Fernandez-Fewell& Meredith, Physiol and Behav, 1995

36. The Terminal nerve: * Is a complex of neurons and nerve fibers that extends from the nasal cavity to the brain along the course of the vomeronasal nerves . * It by-passes the AOB and enters the forebrain behind the olfactory bulbs. * It follows the route by which the precursors of all forebrain GnRH (LHRH) neurons migrate into the brain during embryonic development, and remains in adults as an additional neural connection from nose to brain that is rich in GnRH containing cells and fibers. * The terminal nerve is present in all vertebrates whether or not they have a VNO and it has been suggested that the nerve fibers apparently innervating the human VNO are in fact NT fibers. • NT GnRH neuron terminals ends in the • median eminence.

38. GnRH neurons in the NT project centrally into the ventral forebrain and periphally into the nasal chemosensory mucosa. GnRH receptors are exspressed by chemosensory neurons in VNO and MOE.

39. GnRH alters the response of chemosensory neurons to stimulation by modulation of voltage/receptor gated channels. Using patch clamp technique, GnRH bath increases sodium coductances in olfactory neurones

40. Hypothetical model for GnRH modulation • Neural and hormonal inputs • control the amount of GnRH • available in and secreted by NT GnRH • neurons. • *GnRH diffuses and influences • the response of chemosensory neurons • to odor • *Stimulation of GnRH-R activates second • Messenger pathways that alter the • odor-induced membrane potential and the • signals to be sent to the brain. • *However, the link between NT GnRH and LH • change hasn’t been shown yet.

41. Terminal nerve damage impairs the mating behavior of the male hamster The results are not really convincing…..

42. Take home messages: • Pheromones have a role in supporting reproduction, thus increasing • the chances for successful mating. • Pheromones are not the only factors. Other sensory factors, • memory and learning co-integrate to ensure the success of reproduction. • Pheromones work in accordance with the type of social organization. • The mechanism by which LH secretion is affected is not fully understood • in many of the cases I presented today.