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Evaluation of CNS stimulants: 


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. What is CNS ?

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Central Neurotransmitters :: 

Amino Acids Glutamate GABA Glycine Acetylcholine Monoamines Dopamine Norepinephrine 5-Hydroxytriptamine Peptides Nitric oxide Endocannabinoids Central Neurotransmitters :

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: Analeptics : Doxapram (respiratory stimulant) Nikethamide (respiratory stimulant) Strychnine Picrotoxin Bicuculline What are CNS stimulants ?

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Psychomotor stimulants: Amphetamine Methamphetamine Methylphenidate Cocaine Fenfluramine General cellular stimulants: Methylxanthines derivatives; Caffeine (Coffee) Theophylline (Tea) Theobromine (Chocolate) Clinical antidepressants MAO inhibitors Catecholamine reuptake inhibitors Psychotomimetic (Hallucinogenic )


EVALUATION METHODS : Screening of analeptics by Photoactometer Strychnine induced convulsion Sand displacement method Runway test Ptosis test Duration of anaesthesia Jiggle cage method Tread wheel method Rota rod method Hole board test

Screening of analeptics by Photoactometer:: 

Screening of analeptics by Photoactometer : Purpose : CNS stimulants like Amphetamine increase the locomotor activity in animal, locomotor activity can be an index of wakefulness of mental activity. CNS stimulant – increase activity. Requirements : Animal :mice Sex: either sex Weight: 20-25 gm Age : 8-12 weeks Saline, Amphetamine (1.0mg/kg, I.P.) Procedur e: Animal divided in to 3 groups, (n =4) Control : Saline Standard : Amphetamine (1 mg/kg I.P.) Mice , separately placed in photoactometer for 10 min , after 30 min of drug administration . Photoactometer – circular arena , 6 photocells,30 X30 cm , connected to circuit. Evaluation : No. of “ cut off ” is compared between groups of animal. 8

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Modification: Rat (200-250 gm) used. Inference : Increase in motor activity indicate CNS stimulant property of drug. Digital Photoactometer

Sand displacement method :: 

Sand displacement method : Purpose : Drug like Caffeine stimulate the motoractivity in animal by inhibiting the adenosine transmission in the brain. Requirement : Animal:Mice Sex: either sex Weight:20-25 gm Age:8-12 weeks Saline, caffeine(20 mg/kg, orally) Procedure : A cage with sand is calibrated for amount of sand displaced per unit time. Mice 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.

Runway test :: 

Runway test : Purpose : To study the spontaneous activity of CNS stimulants Requirement: Animal: Wistar rats sex: Female weight: 250-300 gm age:115 to140 days Saline, Amphetamine(2 mg/kg, I.P.) Procedure : animals are grouped(n=8 to 10) 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.) Test : Drug to be evaluated 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, footprints of animal- shows regularity of spacing is a measure of ataxia. Modification: CNS depressant Amylobarbitone (15 mg/kg I.P.)

Runway Apparatus:: 

Runway Apparatus: The apparatus is a symmetrical Y-shaped runway , made up of wood and 13 inches high. Each arm is 15 inches long and 5 inches wide. A trial consists of placing a rat in the center of the Y and leaving it in the apparatus for 5 minutes. The number of times it enters the arms of the apparatus, so that all of its feets are arm, is recorded as a measure of activity. In order to estimate the degree of ataxia, the rat is then placed on a runway covered with paper, so that the record of the footprint’s is obtained. The comparison with the footprint record of a control rat shows that the regularity of spacing is a measure of ataxia.

Ptosis test :: 

Ptosis test : Purpose : Reserpine decreases central sympathetic outflow and leads to ptosis in eye. Requirement: Animal:Albino mice Sex: male Weight:18-24 gm Age:8-12 weeks Saline,Reserpine (4 mg/ kg,I.P .) Procedure : Albino are grouped(n=6) in three groups Reserpine is given in all group (4 mg/kg I.P.) complete ptosis reached after 2 hr 45 min Control : saline Test : drug to be evaluated 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. 13

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Evaluation : 4 for complete ptosis 3 for ¾ ptosis 2 for ½ ptosis 1 for ¼ ptosis Modification: Deoxyephedrine ( 5 mg/kg, I.P.) Cocaine (40 mg/kg, I.P.) Lysergic acid diethylamide (2 mg/kg, I.P.)

Duration of anesthesia :: 

Duration of anesthesia : Purpose : Analeptics produces diminution in duration of anesthesia & also produces respiration stimulation Requirement : Animal: Guinea pig Sex: either sex Weight: 250-700 gm Procedure : Animals are grouped (n= 8 or 10), animal secured in prone position, hair removed from outer surface of forelimbs over the cephalic vein S.C. inject 0.1 ml of a soln. of 2%(w/v) of procaine after 1 min skin region plucked and small Patch is cut exposing 0.6 cm of vein in each forelimbs Given Pentobarbital sodium (50 mg/kg I.P.) and thiopental sodium. Anaesthetic used as soln to 7.5 mg/ml , at the rate of 0.6 ml per minute.

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After infusion about 10 min. Killed the animal with this conc. Of drug. soln injected by fine dental syringe needle into the vein, attached to the motor driven syringe cause respiratory depression 20 seconds elapse between inspiration injection stopped. test compound injected at a rate of 0.6 ml per minute. Animal protected by cotton pledgets and temp. 30 degree. Evaluation : Restorative dose and convulsive dose . Critical assesment : guinea pig cuts are observed after 2 hrs. Animal live for 2 hrs. considerable as survived . Modification: Sprague Dowly Rats can be used.

Jiggle cage method :: 

Jiggle cage method : Purpose : Test is used to evaluate the effect of drug on motor activity of animal. Requirement: Animal: Wistar rat Sex : either sex Weight: 250-300 gm Age: 8- 12 weeks Saline, Methamphetamine (2 mg/kg., I.P.) Procedure : Wistar rats are grouped (n= 6) Control : Saline Standard : Methamphetamine (2 mg/kg I.P.) Test : Drug to be evaluated animal placed in jiggle cage for 10 min to observe activity changes Evaluation : Changes in the movement of animal Modification : Mice can also be used



Tread wheel method :: 

Tread wheel method : Purpose : Effect of drug on locomotor activity of rat Requirement: Animal: Wistar rat Sex: either sex Weight: 250-300 gm Age: 8-12 weeks Saline ,Methamphetamine(2 mg/kg, I.P.) Procedure : Wistar rats are grouped( n= 6) Control : Saline Standard : Methamphetamine (2 mg/kg I.P.) Test : Drug to be evaluated animal placed in tread wheel for 10 min to observe activity changes Evaluation : Changes in the movement (speed of rotation) of animal

Tread Wheel: 

Tread Wheel

Rota road test :: 

Rota road test : Purpose : To evaluate the effect of drug on motor coordination and balance in rodents, animal keep their balance on a rotating rod, measured the time(latency) it takes the mouse to fall off the rod acceleration. Requirement: Animal: Mice Sex: male Weight:18-24 gm Age: 8-12 weeks Saline, Amphetamine (4 mg/kg I.P.) Procedure : Mice are grouped (n=6) in three group, acclimitation time 15 min. Control : saline Standard : Amphetamine (4 mg/kg I.P.) Test : drug to be evaluated After 30 min animal placed on rotarod dm 5 cm.operating speed from 4 to 40 rpm in 300 sec. Evaluation :The time for falling of animal is recorded.




REFERENCES : 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. 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. 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. Rang HP, Dale MM, Ritter JM, and Flower RJ. CNS stimulants and psychotometric drug edited Rang and Dale’s Pharmacology , 6 th Edition, UK: Churchhill Livingstone Elsevier 2007; 610-619. Turner RA, Central stimulants in Screening methods in pharmacology , Academic press Elsevier, 2009;Vol. 1:178-189.

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Pickens R. Behavioral Pharmacology: A brief history. In Advances in Behavioral Pharmacology, edited Thompson T, and Dews PB, Academic Press, 1977; Vol.1:230. Stong CL. An Amateur's Controlled Experiments Measure the Effects of a Tranquilizing Drugs on Rats, Science Project Summary, 1959. Goyal RK, Screening of drugs acting on central nervous system in Practical in pharmacology, 5 th edition, B. S. Shah prakasan , Ahmedabad . 2005-2006:121-137.

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