Neurohumoral transmission involve release from a nerve terminal of a neurotransmitter that react with specialized receptors area on the enervated cell.

1. NEUROHUMORAL TRANSMISSION
,CO-TRANSMISSION
NEUROTRANSMITTER
Miss. D. R. Wagh. M. Pharm.
Asst. Prof. Sveri college of pharmacy,
Pandharpur.

2. INTRODUCTION
• Neurohumaral transmission refers to the transmission of impulse
through synapse and neuro-effector junctions by the release of
humoral (chemical) substances.
• The term conduction stands for the release for the passage of an
impulse along an axon or impulse fibres.
• The transmission of impulses from neuron to neuron or from neuron to
effector organ by means of a neurohumoral substances.

3. Almost all autonomic drugs , which are used clinically , exert their
pharmacological actions by altering essential steps in the neurohumral
transmission process. there are number of other neurotransmitter which
are called as non-adrenergic non-cholinergic transmitters ,released from
the specific nerve endings. Those include nitric oxide , serotonin , ATP ,
dopamine ,GABA , purines , peptides etc.

4. Preganglionic neuron
In the autonomic nervous system . Fibers from the central nervous system to the
ganglion are known as preganglionic fibers . All the preganglionic fibers , whether they
are in the sympathetic nervous system or in the parasympathetic nervous system are
cholinergic these use acetylcholine as their neurotransmitter and are mylinated.
Postganglionic neuron
In the autonomic nervous system , fibers from ganglion to the effector organ are called
postganglionic fibers. The post ganglionic neuron directly responsible for changes in
the activity of the target organ via biochemical modulation and neurotransmitter
releases. They are cholinergic and use acetylcholine as their neurotransmitter.
Synapse
A synaptic connection between a neuron and muscles cell is called a neuromuscular
junction.

5. PHYSIOLOGICAL STEPS INVOLVED IN NEUROHUMORAL TRANSMISSION
Axonal conduction :
• Central system send message or impulse through efferent autonomic nerves.
• A message or impulse is nothing but the state of depolarizing which is
propagated through the nerve fibre for transmission of information through it.
• In normal resting state, a nerve cell is approximately negative inside to the
outside .
• This resting membrane potential of a typical mammalian axon.
• At rest the Na+ concentration is high at high at extracellular space and slow in
intracellular fluid.
• Where the concentration of k ion is nearly 40 fold higher in axoplasm than the
extracellular fluid .
• Though the k ions can cross the resting axonal membrane but Na ion are not
permeable through the membrane.

6. • These ionic gradient or the resting membrane potential is maintained by the energy
dependent active transport.
• Stimulations or arrival of an electrical impulse to a nerve fiber causes a sudden
increase in Na permeability .
• Na enters into the fiber through Na channel and there by increase the positivity
(depolarization) inside the fiber.
Transmitters release:
• The release transmitters rapidly migrate across the cleft and bind with specific
receptors on the junction neuronal or effectors cell membrane .
• The excitatory neurotransmitters bind with their receptors resulting in increase in Na
permeability which causes depolarization followed by k efflux or repolarization .
• Similarly , inhibitory neurotransmitters bind with their respective receptors to increase
the permeability of k and calcium which move in direction of their concentration
gradient resulting hyper polarization(increase negativity inside the cell)

7. Co-transmission:
•In chemical synapse signals are transmitted across the synaptic cleft by means of
chemical messenger (a neurotransmitter) released from the presynaptic axon
terminal.
•Sometimes more than one neurotransmitter may be simultaneously released from
axon.
•The additional neurotransmitters is called as a co-transmitter.
•These neurotransmitters have different receptors on the postsynaptic cell.
Example :
Nor adrenaline , ATP in blood vessels , vas deferens
ACH or vasoactive intestinal peptide in salivary gland

8. CLASSIFICATION OF NEUROTRANSMITTERS
Neurotransmitters are chemical messengers that transmit signals from neuron to the
target cell (neuron ,muscle cell gland across the synapse Neurotransmitters can be
classified as either excitatory or inhibitory. Excitatory neurotransmitters function to
activate receptors on the postsynaptic membrane and enhance the effects of the
action potential, while inhibitory neurotransmitters function in a reverse mechanism.
COMMON TYPE OF NEUROTRANSMITTERS :
Acetylcholine: acetylcholine is the excitatory neurotransmitters occurring through
out the nervous system and is the best understood and studied. It was first
neurotransmitters to be discovered and was isolated in 1921 by a German biologist
named Otto Loewi , who later won a Nobel prize for his work . Acetylcholine has
many functions ranging from the stimulation of muscles , including the muscles of the
gastrointestinal system to vital organ.

9. Nor epinephrine : Norepinephrine , also known as noradrenalin is an
excitatory neurotransmitters secreted by the adrenal gland , it acts to increase
the alertness of nervous system as well as to stimulate the process in the body
. For example it is very important endogenous production of epinephrine . It
was first identified by a swedish biologist in 1946.noradrenaline implicated in
mood disorders such as anxiety in which case its concentration in the body is
abnormally high. Alternatively an abnormally low concentration of it may lead
to an impaired sleep cycle.
Epinephrine: also known as adrenaline , epinephrine is an excitatory
neurotransmitters produced by adrenal gland release into blood stream . It
prepare the body for the fight or flight reaction. That’s means when person is
highly stimulated (fear, anger etc) extra amount of epinephrine are released
into the bloodstream. The release epinephrine increase heart rate the heart
rate , and glucose production from the liver . In this way , the nervous and the
endocrine system prepare the body for dangerous and extreme situation

10. Dopamine: dopamine is considered special type of neurotransmitters because its
effects are both excitatory and inhibitory. It was discovered in the 1950 . It is strongly
associated with reward mechanism in the brain , and drugs such as cocaine, opium ,
heroin and alcohol can temporarily increase level in the blood .
GABA: gama-aminobutyric acid is an inhibitory neurotransmitters isolated in 1950 by
Eugene Robert. An abnormally low secretion of GABA may cause conditions like
anxiety.
Glutamate:glutamate is another neurotransmitters with an excitatory effect and
usually ensures homeostasis with effect of GABA. it is most common
neurotransmitters in the central nervous system however excessive level of it can
be toxic to the nerve cells and may lead to conditions like stroke..
Histamine: Histamine is an produced by basophiles and is found in high
concentration in the blood.