2. About CNS ….
• CNS is made of BRAIN and SPINAL CORD.
• The brain is divided into three parts –
Forebrain, Midbrain, and Hindbrain.
• Spinal cord begins from the brain stems and
extends till the lowest end of backbone
• Brain and Spinal cord mainly responsible for
information processing, imagination, memory
and communication.
3. CNS STIMULANT’S……?
• Imbalance between inhibitory and excitatory processes as in
the brain. CNS stimulant balance the inhibitory and excitatory
action
• CNS Stimulants may be used to reduce tiredness and increase
alertness, competitiveness and aggression.
5. SCREENING METHODS
• Strychnine induced convulsion
• Sand displacement method
• Runway test
• Ptosis test
• Duration of anaesthesia
• Jiggle cage method
• Treadwheel method
• Rotarod method
• Barbiturate induced sleeping time
6. Strychnine induced convulsion
Purpose :
Drugs like strychnine produce convulsion and hyper reflexia
by inhibiting glycin in CNS.
Procedure:
1 Groups of 10 mice of either sex with a weight between 18 and
22 gm
2 mice are injected with 2 mg/kg strychnine nitrate i.p. in std
group and in test group test drug is given
3 after few minutes convulsions are observed
7. •Evaluation :
• Time required to produce convulsion is compared.
• Modifications :
• Some other drugs produce same effects like
• Picotoxin
• Pentylenetetrazole
• Bucuculine
8. Sand displacement method :
• Purpose :
• Drug like Caffeine stimulate the motoractivity in animal by
inhibiting the adenosine transmission in the brain.
• Procedure :
• A cage with sand is calibrated for amount of sand displaced per unit
time.
• Mice weighing 20-25 gm are divided in 3 groups
• Control : saline Standard : caffeine (20 mg/kg orally) Test : drug to be
evaluated
• After 1 hour the animal is placed in cage for 15 min
• Evaluation :
• Volume of sand displaced in each group is compared.
9. Runway test:
Purpose :
To study the spontaneous activity of CNS stimulants
PROCEDURE:
1 Rats of either sex weighing 250-300 gm are grouped
Trained to run in a RUNWAY apparatus for 3 days to achieve
constant time and speed to pass runway
2 Control animal: Saline Standard : Methamphetamine
(2mg/kg I.P.)
Test animal : Drug to be evaluated
3 After 30 min of administration of drug ,test is performed
Evaluation :
Running time from door opening to pressing the goal lever was
recorded using a microcomputer.
10. Ptosis test :
• Ptosis is a drooping or falling of the upper eyelid.
• Purpose :
• Reserpine decreases central sympathetic outflow and leads to
ptosis in eye.
• Procedure:
• Albino mice of either sex weighing 18-24 gm are grouped
• Reserpine is given in all group (4 mg/kg I.P.)
• After 2 hr 45 min standard and control drug is administered.
Control : saline
Standard : Amphetamine (1 mg/kg I.P.)
Test : drug to be evaluated
• After 15 min ptotic rating is made
• EVALUATION :
• Difference between control,standard and test animal is measured.
11. Duration of Anesthesia
• Purpose : Analeptics produces reduction in duration of
anesthesia & also produces respiration stimulation.
• Procedure :
1 Rats weighing 250-350 gm are grouped and Given
Pentobarbital sodium (50 mg/kg I.P.) After 20 min
2 Control : Saline
Standard : Methamphetamine (2 mg/kg I.P.)
Test : Drug to be evaluated
3 After this, animal are placed on its back and recovery from
LRR ( loss of righting response ) is checked when animal had
righted itself 3 times in 1 min.
• Evaluation : Recovery time from LRR is compared.
12. Jiggle cage method
• Purpose :
• Test is used to evaluate the effect of drug on motor activity of
animal.
• Procedure :
1 Wistar rats of either sex weighing 250-300 gm are grouped
2 Control : Saline
3 Standard : Methamphetamine (2 mg/kg I.P.)
4 Test : Drug to be evaluated
5 animal placed in jiggle cage for 10 min to
observe activity changes
Evaluation : Changes in the movement of animal.
13. Tread wheel method :
• Purpose : Effect of drug on locomotor activity of rat
• Procedure :
1 Wistar rats of either sex weighing 250-300 gm are grouped
2 Control : Saline
Standard : Methamphetamine (2 mg/kg I.P.)
Test : Drug to be evaluated
3 animal placed in tread wheel for 10 min to observe activity
changes
• Evaluation : Changes in the movement (speed of
rotation) of animal is notice between control animal and tested
animal
14. Rotarod test :
• Purpose :
To evaluate the effect of drug on motor coordination
• Procedure :
1 Mice weighing 18-24 gm are grouped
2 Control : saline
Standard : Amphetamine (4 mg/kg I.P.)
Test : drug to be evaluated
3 After 30 min Animal placed on rotarod
Evaluation :The time for falling of animal is recorded
15. Barbiturate induced sleeping
time :
• Purpose :
To evaluate the effect of drug on motor coordination
Procedure : M
1 mice weighing 20-30 gm are grouped
2 Control : Distilled water (10 ml/kg I.P)
Standard : caffeine (20 mg/kg S.C)
Test : drug to be evaluated
3 After 30 min Pentobarbitone (40 mg/kg I.P.)
4 Animal are observed for onset and duration of sleeping
Evaluation :
The sleeping time
The sleeping time is the time interval between onset of loss of righting
reflex and regain of righting reflex.
16. REFERENCES :
• H. Gerhard Vogel edition second “drug discovery and
evaluation” Library of Congress Cataloging in Publication (pg.
no.414-461)
• Goyal RK, Screening of drugs acting on central nervous system
in Practical in pharmacology, 5th edition, B. S. Shah prakasan,
pg.no. 121-137.
