Pheromone

Institute of health
Department of biomedical sciences
(medical physiology)
About pheromones by begosew 20191
Seminar presentation on
pheromones
By Begosew M.(BSc)
To Teshome G.(MSc ,ass.t prof…)

Outlines
Introduction to pheromones
Pheromone secreting organs
Characteristics of pheromones
Functional classifications of pheromones
Receptors of pheromones
Mechanism s of action of pheromones

Objectives
At the end of this seminar presentation you should be able
to:-
 Explain about the general overview of pheromones
 Identify the typical characteristics of pheromones
 Identify organs that are responsible to secrete pheromones
 Describe the functional classification of pheromones
 Enumerate the application of pheromones in different
species.

Introduction to pheromones
The term ‘‘pheromone’’ is based on the Greek words
Pheran – to transfer – and Hormon – to excite .
Pheromones are chemical substances released in humans,
insects, and animals to trigger a response or to elicit
speciﬁc behavioral expressions or hormonal changes from
the opposite sex, the same sex or both sexes of the same
species. Karlson P, Luscher,1959

Cont.…
 The importance of pheromones in intra-species
communication has long been known in insects.
 A classical example is bombykol, the sexual attractant
of the butterfly Bombyxmori.
Karl G.etal, 2005

Cont.……
Pheromones are contained in body ﬂuids such as urine,
sweat, specialized exocrine gland secretions, and genital
mucous secretions.

Cont.….
 The steroidal compound androstadi-enone (4,16-
androstadien-3-one) (AND), present in human male
secretions such as sweat, saliva, and semen, has been
implicated as a putative human pheromone.
 AND influences mood, physiological arousal and brain
activity.

Cont.……
Smelling AND maintained significantly higher levels of
cortisol in comparison with smelling a control stimulus
with similar olfactory qualities.
Pheromonal action results a potential therapeutic
mechanism whereby merely smelling synthesized or
purified human chemo-signals may be used to modify
endocrine balance.
Wyart et al.2007

Cont.….
Short-term exposure of males to females also is linked to
increased testosterone (T) in rats, mice, rabbits, bulls,
rams, monkeys and humans.
Taymour M. 2011

Characteristics of pheromones
Pheromones are:-
Ectohormones
Species specific
Released in minute quantity
Effective in small amount
Volatile
Low molecular weight
Mc clintock F ,2000

Classification of pheromones
Pheromones can be divided into two classes according
to the physiological effects they cause in the recipient:
“signal” and “primer “pheromones.
Signal pheromones cause short-term changes such as
the release of neurotransmitters that can directly modify
the recipient’s behavior. Kekan P. etal,2017
 For instance, GnRH molecule functions as a
neurotransmitter in rats to elicit lordosis behaviour.

Cont.…
 Primer pheromones evoke long lasting changes in the
body by influencing the hypothalamic-pituitary-
gonadal axis.
 They are believed to exert their effect by altering the
hypothalamic secretion of GnRH.
Kekan P. etal,2017

Cont.……
The effect of primer pheromones on GnRH allows
pheromones to influence the amount of LH and FSH and
the production of T and E.
It also influences the entire hypothalamic-pituitary-
adrenal axis, which influences behavior by secretion of
neurotransmitter.

Cont.……..
For example, rabbit (mothers) release mammary
pheromones that trigger immediate nursing behavior
by their babies.
Kekan P. etal,2017

Fig1 mechanisms of action of pheromones

Cont.……..
Pheromones can also be differentiated into
 Aggregation pheromones
 Alarm pheromones
 Territorial pheromones
 Trail pheromones
 Sex pheromones.

Aggregation pheromones
Aggregation pheromones function in mate selection,
overcoming host resistance by mass attack, and defense
against predators.
They are among the most ecologically selective pest
suppression methods.
They are nontoxic and effective at very low
concentrations.

Alarm pheromones
 Some species release a volatile substance when
attacked by a predator that can trigger flight (in aphids)
or aggression (in ants, bees, termites) in members of the
same species.
 Plants also release tannin(alarm pheromone) that makes
the plant less appetizing for the herbivore.
Kekan P. etal,2017

Territorial Pheromones
This is one type of pheromone that are important for
Courtship, mating, nesting and food gathering.
In dogs, these pheromones are present in the urine,
which they deposit on landmarks serving to mark the
perimeter of the claimed territory.
cats do possess territorial pheromones.

Trail pheromones
Social insects commonly use trail pheromones.
For example, ants mark their paths with pheromones
consisting of volatile hydrocarbons.
This trail attracts other ants and serves as a guide.
Attract and Kill pheromones
 There is a new generation pheromone called “ attract &
kill” which includes an attractant and a killing agent.

Sex Pheromones
 Sex pheromone is a chemical or a mixture of chemicals
that is secreted outside by an individual and triggers an
immediate response of sexual behavior in the receiving
individual.
 They are mostly originated from females and attract
males for mating.

Sex pheromones cont.….
Pheromones can act as a marker to detect estrus.
The potential implication of pheromones on improving
sexual desire in male is also important.
Pheromones may show similarity and dissimilarity in
genes.

Cont.……
The volatile compounds 1-chlorooctane, 4-methyl phenol,
and 9-octadecenoic acid occurred only during estrus.
It was also revealed that bulls were attracted and exhibited
repeated flehmen behavior toward 4-methyl phenol.
Whereas bulls exhibited penis erection and mounting
response by exposure to 9-octadecenoic acid.

Insect chemoreceptors
Insect chemoreceptor cells are surrounded by sensilla.
They may occur in the antennae, mouthparts and other
structures.
Insect antennae are by far the most common organ of
olfactory reception.
A single antennae may have in more of 8000 sensilla of
different classes which respond to a wide range of
chemical stimuli present in the environment.

Cont.……
fig 2 chemoreception in insects

Application of pheromones
1. Puberty acceleration
2. Estrus induction and estrus synchronization
3. Reduction in postpartum anoestrus
4. Estrus detection by female pheromones
5. Penis erection and enhance the sperm quantity
6. Maternal responsiveness by neonatal pheromones
7. Pheromone therapy

Human pheromones
"My wife could turn to me and she may say, 'Why do you love me?' And I can
with all honesty look her in the eye and say, 'Because our pheromones
matched our olfactory receptors.'" ~ Robin Ince

Human pheromones cont.…..
Pheromones in humans may be present in bodily
secretions such as urine, semen or vaginal secretions,
breast milk and potentially also saliva and breath.
The axillary secretions are originated from eccrine and
apocrine sweat glands and sebaceous glands.
The main components of sweat are simple organic acids
(e.g. E-3-methyl-2-hexenoic acid and 3-methyl-3-
hydroxylhexanoic acid). Stewart, 2007

Cont.….
 Human pheromones include axillary steroids, vaginal
aliphatic acids, and stimulators of the vomeronasal
organ.
 Axillary steroids are produced by the testes, ovaries,
apocrine glands, and adrenal glands.
 They are not biologically active until puberty when sex
steroids influence their activity.

Axillary steroids
Fig 3 structures of axillary steroids

Cont.…..
fig 4 synthesis of steroid pheromones

Axillary steroids cont.…
Androstenol is the putative female pheromone.
 Involves the synchronization of menstrual cycles among
women based on unconscious odor cues(dormitory
effect).
Two types of pheromones are involved:-
"One, produced prior to ovulation, shortens the
ovarian cycle
The second, produced just at ovulation, lengthens the
cycle

Axillary steroids cont.…
Androstenone is postulated to be secreted only by males
as an attractant for women, and thought to be a positive
effector for their mood.
 It has different effects on women, with the highest
sensitivity to it during ovulation.

Cont.….
Androstadienone affects the limbic system and causes a
positive reaction in women, improving mood.
 Responses to androstadienone depends on the individual.
 Androstadienone negatively influences the perception of
pain in women.

Vaginal aliphatic acids
 A class of aliphatic acids was found in female rhesus
monkeys.
 They are six types in the vaginal fluids among these the
acetic acid is one.
 The combination of these acids are referred to as
"copulins“ signals ovulation and sexual
communications.

Odour-producing organ
In humans the main odour-producing organ is the skin
through its apocrine and sebaceous glands.
This gland develops during puberty and are associated
with sweat glands and tufts of hairs.
These glands are mainly concentrate in areas like axillae,
nipples, pubic, genital, circum-anal, circum-oral region,
lips, the eyelids and the outer ear. Stewart, 2007

Cont.…..
Substances produced by these glands are relatively
imperceptible to the human nose.
What are smelled are not the original glandular secretions
but rather their bacterial breakdown products.
Urine and faeces are also other potentially important
odour sources.

MOLECULAR BASIS OF PHEROMONE AND
ODOR SENSATION
Mammalian pheromones are detected by the olfactory
system including the main olfactory epithelium (MOE)and
vomeronasal organ (VNO).
 Sensory neurons located in these various olfactory tissues
express different repertoires of chemosensory receptors
and signaling molecules, project axons to discrete target
regions of the olfactory bulb, and stimulate distinct limbic
circuits.

Cont.….
Pheromones are released into the environment as small
hydrophobic airborne chemicals.
Then it binds with odorant binding protein (OBP).
After binding, OBP delivers the pheromones and
activate the dendrite microvilli of bipolar chemosensory
neuron receptors in VNOs.
The VNO neurons have the ability to encode stimulus
strength.

Cont.………
When the stimulation reaches to its threshold, it activates
the entire subpopulation of neurons to reach action
potential threshold and conduct a strong electro chemical
signal to the brain.
This signal could directly stimulate the hypothalamus to
exhibit an appropriate neuro-endocrine response unique
to the specific subpopulation of neurons stimulated in
VNO.

Fig 5 human vomeronasal organ

Fig 6 the vomero nasal organ and MOE

Fig 7 olfactory pathway

Fig 8 olfactory pathway

Fig 9 signaling mechanism of olfactory receptor

Pheromonal receptors
The human trace amine-associated receptors are a
group of six G protein-coupled receptors (i.e. 1,2,5,6,8
and 9) that – with exception for TAAR1 – are expressed
in the human olfactory epithelium.
In humans and other animals, TAARs in the olfactory
epithelium function as olfactory receptors that detect
volatile amine odorants, including certain pheromones.

Con..…..
o It is noted that the behavioral response evoked by a
TAAR can vary across species (e.g., TAAR5 mediates
attraction to trimethylamin in mice and aversion to
trimethylamine in rats).
o In humans, hTAAR5 presumably mediates aversion to
trimethylamine, which is known to act as an hTAAR5
agonist and to possess a foul, fishy odor that is aversive to
humans. Mariana f ,1998

Receptors in the vomero nasal organ
 An active role for the human VNO in the detection of
pheromones is disputed; while it is clearly present in the
fetus it appears to be atrophied, shrunk or completely
absent in adults.
 Three vomeronasal receptors are identified in the
vomeronasal organ named V1Rs, V2Rs, and V3Rs.
 All are G protein-coupled receptors.
Mariana f ,1998

Fig 10 pathway of impulse from the VNO and MOE

Application of human pheromones
1. Menstrual synchronization
2. Implications for Fertility and Depression

Summary
Human pheromones are poorly studied than other species.
Beutiness is not only determined by vision but also by smell.
Chemicals that function as primer and releaser pheromones that
control aggression, sex, suckling, and maternal behaviors have
been reported..
Pheromones activate neural circuits in the limbic system that can
be hormone modulated, resulting in sex-specific or state-
dependent responses.

references.docx

THANKS FOR YOUR ATTENTION!!!

Pheromone

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