1. CNS Stimulant Drugs 322 PHL 3rd Lecture T.A Samiah
King Saud University College Of Pharmacy Department of Pharmacology
CNS Stimulant Drugs
322 PHL 3rd Lecture T.A Samiah

2. pharmacological experiments
In vitro
Isolated tissue
Adv:
determination exact MOA & the potency of the drug
In vivo
Whole animal or intact animal
Adv:
observation of the clinical effect of drugs
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3. CNS Stimulante Drugs
Anatomy of The Brain
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4. Anatomical features of CNS
Cerebellum+Pons → Equilibrium & coordination of movement
Medulla oblongata → contain vital center e.g. respiratory and cardiovascular centers
Spinal cord → Responsible for all reflexes
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5. Classification of Drugs Acting on CNS
CNS Stimulante Drugs
Classification of Drugs Acting on CNS
Drugs acting on CNS
CNS
depressants
CNS
stimulants
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6. CNS Stimulants Definition:
They are drugs which increase the muscular (motor) and the mental (sensory) activities.
Their effects vary from the increase in the alertness and wakefulness (as with caffeine) to the production of convulsion ( as with strychnine) and sometimes lead to death due to over stimulation.
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7. Classification of CNS stimulants:
Cerebral stimulants.
Psychomotor stimulants e.g. Amphetamine
Medullary stimulants.
Psychotomimetic stimulants (hallucinogenic drugs) e.g. Cannabis, LSD (lysergic acid diethylamine), THC
(tetrahydrocannabinol).
Spinal cord stimulants.
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8. General Signs & Symptoms of CNS Stimulation
↑ Heart rate
↑ Respiratory rate
Instability & restlessness
Muscle twitching (tremors)
Hair erection
Convulsion
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9. Classification of CNS Stimulants According to Their Site of action
Cerebral stimulants
Brain stem ( Pons & medulla) stimulants
Spinal cord stimulants
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10. 1- Cerebral Stimulants Caffeine & Cocaine Examples Cerebral cortex
Site of the action
It inhibits phosphodiesterase enz. → ↑ cAMP
↑calcium in CNS & heart→ excitation
↓calcium in Smooth muscles→ relaxation
2. A2 receptors antagonist → CNS stimulation & smooth muscles relaxation
MOA
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11. 1- Cerebral Stimulants Hair erection Tail erection (onset of action)
End point
epileptiform type of convulsion
High Dose
Decapitation & Pithing
Removed by
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12. 2- Medullary Stimulants
Picrotoxin, Coramine ,Cardiazole
Example
Medulla oblongata
Site of the action
1- Non-competitive GABAA antagonist
2- Block Cl- channel associated with GABAA receptors lead to blocking the postsynaptic inhibitory effect of GABA. So, no hyper-polarization . →excitation
MOA of ( picrotoxin )
Clonic convulsion
End point
Decapitation
Removed by
Samiah.m.Alshehri

13. 3-Spinal Cord Stimulants
Strychnine
Example
Spinal cord
Site of the action
1- Block the postsynaptic inhibitory response to glycine by blocking glycine receptors in spinal cord .
glycine is the main inhibitory transmitter acting on motor neurons
MOA
tonic convulsion
End point
Pithing
Removed by
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14. Differences Between Clonic & Tonic Convulsions
Produced by ↑dose of spinal cord stimulants
Symmetric(both sides convulsed at the same time)
uncoordinated (both flexors and extensors contract)
Reflex in origin (need for external stimuli)
Continuous
Removed by pithing
- Opisthatenous Posture”
(Arched Back
Produced by ↑dose of medullary stimulants
Asymmetric(when the left side of the body convulsed the right side relaxed)
Coordinated (when the flexors contract the extensors relaxed)
Spontaneous in origin(convulsion develop by its own)
Intermittent
Removed by decapitation
It starts as clonic then converted into tonic-clonic and finally to tonic.
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15. Opisthatenous posture
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16. Lab work ROA Dose Conc Drug IP 100 mg/kg 1% Caffeine 5 mg/kg 0.1%
Strychnine
25 mg/kg
0.5%
Picrotoxin
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17. Calculation
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18. Thank You
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