This document describes various methods used to screen drugs that act on the central nervous system (CNS). It discusses CNS stimulants and their ability to balance inhibitory and excitatory processes in the brain. Several classification types of CNS stimulants are provided, including analeptics, psychomotor stimulants, general cellular stimulants, and clinical antidepressants. Eight screening methods are then outlined in detail, including strychnine induced convulsion, sand displacement, runway test, ptosis test, duration of anesthesia, jiggle cage, treadwheel, and rotarod tests. Each method is designed to evaluate specific effects of test drugs on motor function, activity, or coordination in animal models

1. CNS Stimulants
(SCREENING MODELES)
Prepared by –Sachin Jangra
M.PHARM (pharmacology)
Roll no.- 03

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.

4. CLASSIFICATION
1. Analeptics (convulsant)
• Doxapram (respiratory stimulant)
• Strychnine
• Picrotoxin
2. Psychomotor stimulants
• Amphetamine & Methamphetamine
• Methylphenidate
• Cocaine
3. General cellular stimulants
• Caffeine (Caffee)
• Theophylline (Tea)
• Theobromine (Chocolate)
4. Clinical antidepressants
• Catecholamine reuptake inhibitors

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.

17. THANK YOU…….