CNS Stimulant
Content
CNS Stimulants
•
CNS
Stimulants
•
Drugs
act as an CNS stimulant
•
Pharmacology
of CNS Stimulants
•
Adverse
effects
Intended Learning Outcomes
At the
end of this lecture, student will be able to
• Describe
CNS Stimulants
Nervous
System
• Nervous
system can be classified into
• Central
Nervous System (CNS) Brain and spinal cord
• Peripheral
Nervous System (PNS( The nervous system outside of the brain
and spinal cord
Peripheral
Nervous System (PNS)
Divided in to
1- Sensory division (afferent)
• Conducts
impulses from receptors to the CNS and Informs the CNS of the state of the body
2- Motor division (efferent)
• Conducts
impulses from CNS to effectors organs
Motor
Neurons
• The
motor division is also divided into
1- Somatic nervous system:
• VOLUNTARY
(generally) Somatic nerve fibers that conduct impulses from the CNS to skeletal
muscles
2 – Autonomic nervous system:
• INVOLUNTARY (generally) Conducts impulses from
the CNS to smooth muscle, cardiac muscle, and glands
Neurons
• They
are the basic functional unit of the nervous system.
• They
contain three major parts:
1. Cell
body
2.
Dendrites
3. Axon
Neurotransmitters CNS
They can be classified into:
1. Excitatory:
• Ach,
glutamate, aspartate, serotonin and NE.
2. Inhibitory:-
• GABA
, glycin
CNS Stimulants
Definition
• “Stimulants
are a substance which tends to increase behavioral activity when administered”
They can be divided based on their site of action:
• Cerebral
stimulants (Amphetamines)
• Medullary
stimulants (Picrotoxin)
• Spinal
stimulants (Strychnine)
Signs and
symptoms
• Elevate
Mood
• Increase
Motor Activity
• Increase
Alertness
• Decrease
need for Sleep
In
case of overdose lead to convulsion and death
MOA of CNS Stimulants
• Block
neurotransmitters reuptake (Most reuptake inhibitors affect either NE or
5-HT(Serotonin): Cocaine
• Promote
neurotransmitters release : Amphetamine
• Block
Metabolism – MAO inhibitors (monoamine oxidase): ex. Phenelzine
• Antagonize
the effect of inhibitory neurotransmitter: Picrotoxin & Strychnine
Amphetamine
MOAs:
• Block
the reuptake of norepinephrine and dopamine into the presynaptic neuron and
increase the release of these monoamines into the extra neuronal space.
Clinical use:
• Narcolepsy
• Attention-deficit
hyperactivity disorder
Adverse effects:
• Cardiovascular:
Hypertension
• Endocrine
metabolic: Weight loss
• Gastrointestinal:
Abdominal pain, Loss of appetite, Xerostomia.
• Neurologic:
Headache, Insomnia.
• Psychiatric:
Feeling nervous.
After injecting, the mice with amphetamine you will
notice:
• Hair
erection
• Licking
• Stereotype
• Sniffing
Picrotoxin
MOA:
• Non-competitive
antagonist of GABA receptors.
• After
injecting the mice with picrotoxin you will notice:
– Clonic convulsion characterized by:
• Asymmetric
• Intermittent
• Spontaneous
• Coordinated
Strychinine
(Nux vomica)
MOA:
• Competitive
antagonist of the glycin receptors
After injecting the mice with Strychinine you will
notice:
Tonic convulsion characterized by:
• Symmetric
• Reflex
in origin
• Continuous
• Uncoordinated
Summary
• CNS
Stimulants are different from antidepressants
• Act
through excitatory neurotransmitters
• Caffeine and amphetamine are the
main drugs in this category
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