autacoid

1. Aut
acoids
Autacoids are biological factors
which act like local hormones, have
a brief duration, act near the site of
synthesis, and are not blood borne.
Autacoids are primarily
characterized by the effect they have
upon smooth muscle. With respect
to vascular smooth muscle, there are
both vasoconstrictor and vasodilator
autacoids.
Vasodilator autacoids can be
released during periods of exercise.
Their main effect is seen in the skin,
allowing for heat loss.
The word autacoids comes from the
Greek "Autos" (self) and "Acos"
(drug). These are local hormones,
therefore have a paracrine effect.
Some notable autacoids are:
eicosanoids, angiotensin,
neurotensin, NO (nitric oxide),
kinins, histamine, serotonin,
endothelins, etc.
Se
rotonin
Serotonin (pronounced /ˌsɛrə
ˈtoʊnən/) is a monoamine
neurotransmitter that is primarily
found in the gastrointestinal (GI)
tract and central nervous system
(CNS) of animals. Approximately 80
percent of the human body's total
serotonin is located in the
enterochromaffin cells in the gut,
where it is used to regulate intestinal
movements. The remainder is
synthesized in serotonergic neurons

2. in the CNS where it has various
functions, including the regulation of
mood, appetite, sleep, muscle
contraction, and some cognitive
functions including memory and
learning; and in blood platelets
where it helps to regulate hemostasis
and blood clotting. serotonin stored
in platelets is active wherever
platelets bind, as a vasoconstrictor to
stop bleeding, and also as a fibrocyte
mitotic, to aid healing.
Hi
stamine
Most histamine in the body is
generated in granules in mast cells
or in white blood cells called
basophils. Mast cells are especially
numerous at sites of potential injury
- the nose, mouth, and feet, internal
body surfaces, and blood vessels.
Non-mast cell histamine is found in
several tissues, including the brain,
where it functions as a
neurotransmitter. Another important
site of histamine storage and release
is the enterochromaffin-like (ECL)
cell of the stomach.
mechanism of action
Histamine exerts its actions by
combining with specific cellular
histamine receptors. The four
histamine receptors that have been
discovered are designated H1
through
Type Location Function
H1 Found on Causes vasodilation,

3. bronchoconstriction,
bronchial smooth
muscle contraction,
separation of
smooth
endothelial cells
muscle,
(responsible for
histamine endothelium,
hives), and pain and
receptor and central
itching due to insect
nervous
stings; the primary
system tissue
receptors involved in
allergic rhinitis
symptoms and
motion sickness.
H2
Located on Primarily stimulate
histamine
parietal cells gastric acid secretion
receptor
Found on
central
Decreased
nervous
neurotransmitter
H3 system and to
release: histamine,
histamine a lesser
acetylcholine,
receptor extent
norepinephrine,
peripheral
serotonin
nervous
system tissue
Found
primarily in
the basophils
and in the
bone
H4
marrow. It is Plays a role in
histamine
also found on chemotaxis.
receptor
thymus,
small
intestine,
spleen, and
colon.
A
ngiotensin

4. Angiotensin, a protein, causes blood
vessels to constrict, and drives blood
pressure up. It is part of the renin-
angiotensin system, which is a major
target for drugs that lower blood
pressure. Angiotensin also
stimulates the release of aldosterone
from the adrenal cortex. Aldosterone
promotes sodium retention in the
distal nephron, in the kidney, which
also drives blood pressure up.
Neurotensin is a 13 amino acid
neuropeptide that is implicated in the
regulation of luteinizing hormone
and prolactin release and has
significant interaction with the
dopaminergic system. Neurotensin
was first isolated from extracts of
bovine hypothalamus based on its
ability to cause a visible vasodilation
in the exposed cutaneous regions of
anesthetized rats.
E
ndothelins
Endothelins are proteins that
constrict blood vessels and raise
blood pressure. They are normally
kept in balance by other
mechanisms, but when they are
over-expressed, they contribute to
high blood pressure (hypertension)
and heart disease.
Endothelins are 21-amino acid
vasoconstricting peptides produced
primarily in the endothelium having
a key role in vascular homeostasis.
Among the strongest
vasoconstrictors known, endothelins
are implicated in vascular diseases
of several organ systems, including
the heart, general circulation and
brain.[1

5. There are three isoforms (identified
as ET-1, -2, -3) with varying regions
of expression and two key receptor
types, ETA and ETB.
• ETA receptors are found in
the smooth muscle tissue of
blood vessels, and binding of
endothelin to ETA increases
vasoconstriction (contraction
of the blood vessel walls)
and the retention of sodium,
leading to increased blood
pressure.[3]
• ETB is primarily located on
the endothelial cells that line
the interior of the blood
vessels. When endothelin
binds to ETB receptors, this
leads to the release of nitric
oxide (also called "NO" or
endothelium-derived relaxing
factor), natriuresis and
diuresis (the production and
elimination of urine) and
mechanisms that lower blood
pressure.
• Both types of ET receptor are
found in the nervous system
where they may mediate
neurotransmission and
vascular functions.[4]
•
Eico
csanoid
Pathways in biosynthesis of
eicosanoids from arachidonic acid:
there are parallel paths from EPA &
DGLA.
In biochemistry, eicosanoids are
signaling molecules made by
oxidation of twenty-carbon essential
fatty acids, (EFAs). They exert

6. complex control over many bodily
systems, mainly in inflammation or
immunity, and as messengers in the
central nervous system. The
networks of controls that depend
upon eicosanoids are among the
most complex in the human body.
Eicosanoids derive from either
omega-3 (ω-3) or omega-6 (ω-6)
EFAs. The ω-6 eicosanoids are
generally pro-inflammatory; ω-3's
are much less so. The amounts and
balance of these fats in a person's
diet will affect the body's
eicosanoid-controlled functions,
with effects on cardiovascular
disease, triglycerides, blood
pressure, and arthritis. Anti-
inflammatory drugs such as aspirin
and other NSAIDs act by
downregulating eicosanoid
synthesis.
Function and
pharmacology
Metabolic actions of selected prostanoids and
leukotrienes†[15]
Stimulation of
platelet
PGD2 Promotion of sleep TXA2
aggregation;
vasoconstriction
Smooth muscle
contraction;
Adipocyte
PGE2 inducing pain, heat, 15d-PGJ2
differentiation
fever;
bronchoconstriction
Leukocyte
PGF2α Uterine contraction LTB4
chemotaxis
PGI2 Inhibition of platelet Cysteinyl- Anaphylaxis;

7. aggregation; bronchial
vasodilation; smooth
LTs
embryo muscle
implantation contraction.
†
Shown eicosanoids are AA-derived; EPA-derived generally have
weaker activity
.
Role in inflammation
Since antiquity, the cardinal signs of
inflammation have been known as:
calor (warmth), dolor (pain), tumor
(swelling) and rubor (redness). The
eicosanoids are involved with each
of these signs.
Redness—An insect's sting will
trigger the classic inflammatory
response. Short acting
vasoconstrictors — TXA2—are
released quickly after the injury. The
site may momentarily turn pale.
Then TXA2 mediates the release of
the vasodilators PGE2 and LTB4.
The blood vessels engorge and the
injury reddens.
Swelling—LTB4 makes the blood
vessels more permeable. Plasma
leaks out into the connective tissues,
and they swell. The process also
looses pro-inflammatory cytokines.
Pain—The cytokines increase
COX-2 activity. This elevates levels
of PGE2, sensitizing pain neurons.
Heat—PGE2 is also a potent pyretic
agent. Aspirin and NSAIDS—drugs
that block the COX pathways and
stop prostanoid synthesis—limit
fever or the heat of localized
inflammation.

8. Action of prostanoids
Prostanoids mediate local symptoms
of inflammation: vasoconstriction or
vasodilation, coagulation, pain and
fever. Inhibition of cyclooxygenase,
specifically the inducible COX-2
isoform, is the hallmark of NSAIDs
(non-steroidal anti-inflammatory
drugs), such as aspirin. COX-2 is
responsible for pain and
inflammation, while COX-1 is
responsible for platelet clotting
actions.
Prostanoids activate the PPARγ
members of the steroid/thyroid
family of nuclear hormone receptors,
directly influencing gene
transcription.[21]
Action of leukotrienes
Leukotrienes play an important role
in inflammation. There is a
neuroendocrine role for LTC4 in
luteinizing hormone secretion.[22]
LTB4 causes adhesion and
chemotaxis of leukocytes and
stimulates aggregation, enzyme
release, and generation of
superoxide in neutrophils.[23]
Blocking leukotriene receptors can
play a role in the management of
inflammatory diseases such as
asthma (by the drugs montelukast
and zafirlukast), psoriasis, and
rheumatoid arthritis.
The slow reacting substance of
anaphylaxis comprises the cysteinyl
leukotrienes. These have a clear role
in pathophysiological conditions
such as asthma, allergic rhinitis and
other nasal allergies, and have been
implicated in atherosclerosis and
inflammatory gastrointestinal
diseases.[24] They are potent
bronchoconstrictors, increase
vascular permeability in

9. postcapillary venules, and stimulate
mucus secretion. They are released
from the lung tissue of asthmatic
subjects exposed to specific
allergens and play a
pathophysiological role in
immediate hypersensitivity reactions
Along with PGD, they function in
effector cell trafficking, antigen
Enteric nervous
system
The enteric nervous system (ENS)
is a subdivision of the Peripheral
Nervous System, that directly
controls the gastrointestinal
system.drived from neuralcrest
Function
The ENS is capable of autonomous
functionssuch as the coordination of
reflexes, although it receives
considerable innervation from the

10. autonomic nervous system and thus
is often considered a part of the
ANS. Its study is the focus of
neurogastroenterology. The ENS can
be damaged by ischemia.
Transplantation has been described
as a theoretical possibility.
Anatomy
The ENS consists of some one
hundred million neurons one
thousandth of the number of neurons
in the brain, and considerably more
than the number of neurons in the
spinal cord. The enteric nervous
system is embedded in the lining of
the gastrointestinal system.
The neurons of the ENS are
collected into two types of ganglia:
myenteric (Auerbach's) and
submucosal (Meissner's) plexuses
Myenteric plexuses are located
between the inner and outer layers of
the muscularis externa, while
submucosal plexuses are located in
the submucosa.
Complexity
The enteric nervous system has been
described as a "second brain" There
are several reasons for this. The
enteric nervous system can operate
autonomously. It normally
communicates with the CNS through
the parasympathetic (eg, via the
vagus nerve) and sympathetic (eg,
via the prevertebral ganglia) nervous
systems. However, vertebrate studies
show that when the vagus nerve is
severed, the enteric nervous system
continues to function.
In vertebrates the enteric nervous
system includes efferent neurons,
afferent neurons, and interneurons,
all of which make the enteric
nervous system capable of carrying

11. reflexes and acting as an integrating
center in the absence of CNS input.
The sensory neurons report on
mechanical and chemical conditions.
Through intestinal muscles, the
motor neurons control peristalsis and
churning of intestinal contents.
Other neurons control the secretion
of enzymes. The enteric nervous
system also makes use of more than
30 neurotransmitters, most of which
are identical to the ones found in
CNS, such as acetylcholine,
dopamine, and serotonin. The
enteric nervous system has the
capacity to alter its response
depending on such factors as bulk
and nutrient composition. In
addition, ENS contains support cells
which are similar to astroglia of the
brain and a diffusion barrier around
the capillaries surrounding ganglia
which is similar to the blood-brain
barrier of cerebral blood vessels.[10]
The myenteric The plexus of the
plexus from the submucosa from
rabbit. X 50. the rabbit. X 50.

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