Evaluation of CNS Stimulants

Presented by:Mr. Nirav S. VachhaniM.Pharm Pharmacology (Sem-

II)

EVALUATION METHODS FORCNS

STIMULANTS

Guided by:

Dr. Rina H. Gokani(Associate professor)

S. J. Thakkar pharmacy college, Rajkot.

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What is 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• Both the brain and spinal cord contain fluid filled spaces or cavities. The fluid in these spaces is called cerebrospinal fluid (CSF), and contains nutrients, hormones, white blood cells to maintain the CNS.• Brain and Spinal cord mainly responsible for information processing, imagination, memory and communication.

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BRAIN

&

SPINAL C

ORD

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Central Neurotransmitters :• Amino Acids• Glutamate

• GABA

• Glycine

• Acetylcholine• Monoamines• Dopamine

• Norepinephrine

• 5-Hydroxytriptamine

• Peptides• Nitric oxide• Endocannabinoids

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What are CNS stimulants ?

• Central Nervous System Stimulants may be used to reduce tiredness and increase alertness, competitiveness and aggression.• CNS stimulants may be defined as “Drug substance that most specifically afford an enhancement in excitability either very much within the different portions of the brain or the spinal cord which may lead to convulsion.”• CNS stimulants may be classified as below:

1.Analeptics (convulsant)• Doxapram (respiratory stimulant)

• Nikethamide (respiratory stimulant)

• Strychnine

• Picrotoxin

• Bicuculline

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2.Psychomotor stimulants• Amphetamine & Methamphetamine

• Methylphenidate

• Cocaine

• Phentemine

• Fenfluramine

3.General cellular stimulants• Methylxanthines derivatives• Caffeine (Caffee)• Theophylline (Tea)• Theobromine (Chocolate)

4.Clinical antidepressants• MAO inhibitors• Catecholamine reuptake inhibitors

5.Psychotomimetic (Hallucinogenic)

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EVALUATION METHODS :1. Screening of analeptics by PHOTOACTOMETER

2. Strychnine induced convulsion

3. Sand displacement method

4. Runway test

5. Ptosis test

6. Duration of anaesthesia

7. Jiggle cage method

8. Treadwheel method

9. Rotarod method

10.Barbiturate induced sleeping time

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1.Screening of analeptics by PHOTOACTOMETER

• Purpose : CNS stimulants like Amphetamine increase the locomotor activity in animal.• Procedure : Mice weighing 20-25 gm are divided in in to 3 groups, each contain 4 animals.

Control : Saline

Standard : Amphetamine (1 mg/kg I.P.)

Test : Drug to be evaluated

Mice from each group, separately placed in photoactometer for 10 min duration at

the intervals of 30 min till the maximum effect of drug is observed.

• Evaluation : No. of “ cut off ” is compared between groups.

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Digital Photoactometer

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2. Strychnine induced convulsion• Purpose : Drugs like strychnine produce convulsion and

hyperreflexia by inhibiting glycin in CNS.• Procedure : Groups of 10 mice of either sex with a weight between 18 and 22 gm

mice are injected with 2 mg/kg strychnine nitrate i.p. in std group and in test group test drug is given

after few minutes convulsions are observed• Evaluation : Time required to produce convulsion is compared.•Modifications : Some other drugs produce same effects like

Picotoxin

Pentylenetetrazole

Bucuculine


3. 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.


4. Runway test :• Purpose : To study the spontaneous activity of CNS stimulants• Process : Wistar 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

Control : Saline

Standard : Methamphetamine (2 mg/kg I.P.)


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.

Runway Apparatus:• The runway apparatus, made using a 5 mm acrylic board, consisted of a start box (26.5-cm wide, 26-cm long, and 30-cm high),• A controlled start door (26.5- cm wide, and 30-cm high) that opened by dropping down a runway (18-cm wide, 180-cm long, and 30-cm high),• Priming box (30x30x30 cm).• A retractable lever (the goal lever) was set at the end of the runway 7 cm above the floor.• Stimulation was provided from constant current stimulators in the form of 0.2 ms pulses of 60 Hz alternating current. The stimulation current was individually adjusted for each rat.


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5. Ptosis test :• 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

Control : saline



After 15 min ptotic rating is made• Evaluation : 4 for complete ptosis

3 for ¾ ptosis

2 for ½ ptosis

1 for ¼ ptosis© SJTPC, Rajkot.


6. Duration of anesthesia :• Purpose : Analeptics produces diminution in duration of anesthesia & also produces respiration stimulation• Procedure : SD rats weighing 250-350 gm are grouped and

Given Pentobarbital sodium (50 mg/kg I.P.)

After 20 min

Control : Saline



After this, animal are placed on its back and recovery from LRR is checked when animal had righted itself 3 times in 1 min• Evaluation : Recovery time from LRR is compared•Modifications :Guinea pig, Rabbit, Mice, Monkey, Cat


7. Jiggle cage method :• Purpose : Test is used to evaluate the effect of drug on motor activity of animal.• Procedure : Wistar rats of either sex weighing 250-300 gm are grouped

Control : Saline



animal placed in jiggle cage for 10 min to observe activity changes• Evaluation : Changes in the movement of animal•Modification : Rat can also be used


JIGGLE CAGE


8. Tread wheel method :• Purpose : Effect of drug on locomotor activity of rat• Procedure : Wistar rats of either sex weighing 250-300 gm are grouped

Control : Saline



animal placed in tread wheel for 10 min to observe activity changes• Evaluation : Changes in the movement (speed of rotation) of animal•Modification : Rat can also be used


Tread Wheel


Tread Wheel


9. Rota road test :• Purpose : To evaluate the effect of drug on motor coordination• Procedure : Mice weighing 18-24 gm are grouped

Control : saline



After 30 min

Animal placed on rotarod• Evaluation :The time for falling of animal is recorded


Rotarod


10.Barbiturate induced sleeping time :• Purpose : To evaluate the effect of drug on motor

coordination• Procedure : Mice weighing 20-30 gm are grouped

Control : Distilled water (10 ml/kg I.P)

Standard : caffeine (20 mg/kg S.C)


After 30 min

Pentobarbitone (40 mg/kg I.P.)

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.


REFERENCES :1. Owolabi OJ, Amaechina FC, and Eledan AB. Central

nervous system stimulant effect of the ethanolic extract of Kigelia africana, Journal of Medicinal Plants Research, 2008;Vol. 2(2):20-23.

2. Anders A, Medrano A, Garrido N,and Alonso P. GABAergic Drugs Inhibit Amphetamine-Induced Distractibility in the Rat, Pharmacology Biochemistry and Behavior, 1997;Vol. 58(1):119–126.

3. Garberg L, and Sandberg F. A Method for Quantitative Estimation of the Stimulant Effect of Analeptics on the Spontaneous Motility of Rats, Acta pharmacology and toxicology, 1960;Vol. 16:367-373.

4. Rang HP, Dale MM, Ritter JM, and Flower RJ. CNS stimulants and psychotometric drug edited Rang and Dale’s Pharmacology, 6th Edition, UK: Churchhill Livingstone Elsevier 2007; 610-619.

5. Turner RA, Central stimulants in Screening methods in pharmacology, Academic press Elsevier, 2009;Vol. 1:178-189.


6. Pickens R. Behavioral Pharmacology: A brief history. In Advances in Behavioral Pharmacology, edited Thompson T, and Dews PB, Academic Press, 1977; Vol.1:230.

7. Stong CL. An Amateur's Controlled Experiments Measure the Effects of a Tranquilizing Drugs on Rats, Science Project Summary, 1959.

8. Goyal RK, Screening of drugs acting on central nervous system in Practical in pharmacology, 5th edition, B. S. Shah prakasan, Ahmedabad. 2005-2006:121-137.

Thank

You

Evaluation of CNS Stimulants

Education

test group test drug

runway test

time sjtpc

ptosis test

digital photoactometer

runway control

drug substance

runway apparatus