CNS Stimulant – Pharmacology B. Pharma 5th Semester PDF Notes

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

Neuron

       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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