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

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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