PHEROMONES AND THE MENSTRUALESTRUS CYCLE

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PHEROMONES AND THE MENSTRUAL/ESTRUS CYCLE
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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.
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While most mammals have VNO in addition to the
olfactory organ, humans Lack it.
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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
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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.
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flank marking hamster
Mating behavior rat male
Plural breeder Rodents, humans
Singular breeders Marmosets
The male effect ewe
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Social and reproductive strategies Plural
breeding VS. Singular breeding
Marmosets
Rats, Humans
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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.
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Plural Breeders
Humans
The most known phenomenon between females is the
Cycling Synchronization Effect
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The coupled oscillator mechanism
Ovulatory pheromone lengthens cycle, and
follicular pheromone shortens cycle (Stern
McClintock, 1998).
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Ovulatory phase pheromones lengthen Follicular
stage
Follicular phase pheromones shorten Follicular
and luteal phases.
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In rats All female environment tends to
suppress the estrus cycle
Induction of spontaneous pseudopregnancy
Extension of estrus cycle
Prolongation of quiescent period
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?
However, although the phenomenon are well
described, the neuroendocrine correlates of
female to female effect in plural breeding group
species havent been published.
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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.
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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.
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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
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Male and female pheromonal interaction
Humans

• Pheromonal related neuroendocrine changes in
  humans brain havent 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.

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

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Number of flank marks are more frequent in
diestrus2 and proestrus and low in diestrus1 and
estrus stages.
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E replacement to OVX females restores cyclicity
of flank marks
Progesterone addition inhibits the stimulatory
effect of E
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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
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V1R antagonist inhibits the AVP induction effect.
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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.
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Based on observation in rats and mice E induces
number of AVP-R (AVP 1aR) (not yet in hamster).
Rat mPOA
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• 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.

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

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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
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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.

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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.
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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
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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 hasnt been shown yet.

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