Anti epileptic drugs screening methods including invitro and invivo screening methods includes isoniazid picrotoxin strychrinine and Pentenlytetrazole induced convulsion

1. ANTIEPILEPTIC
SCREENING
METHODS
KRVS Chaitanya

2. 1. PENTYLENE TETRAZOLE
(METRAZOL) INDUCED
CONVULSIONS

3. 1. PENTYLENETETRAZOLE (METRAZOL)
INDUCED CONVULSIONS
PURPOSE AND RATIONALE
• This assay has been used primarily to evaluate
antiepileptic drugs.
• However, it has been shown that most anxiolytic agents
are also able to preventor antagonize Metrazol-induced
convulsions.

4. PROCEDURE
•Mice of either sex with a body weight between 18
and 22g are used.
•The test compound or the reference drug is injected
sc. or i.p. or given orally to groups of 10mice.
•Another group of 10mice serves as control.

5. •Fifteen min after sc.-injection, 30min after i.p.injection,
or 60min after oral administration 60mg/kg
MTZ(Metrazol)are injected subcutaneously.
•Each animal is placed into an individual plastic cage for
observation lasting 1h.

6. •Seizures and tonic-clonic convulsions are recorded.
•At least 80% of the animals in the control group have
to show convulsions.

7. EVALUATION
•The number of protected animals in the treated groups
is calculated as percentage of affected animals in the
control group.
•ED50-values can be calculated.

8. •Further more, the time interval between MTZ-
injection and occurrence of seizures can be
measured.
•The delay of onset is calculated in comparison with
the control group.

9. CRITICAL ASSESSMENT OF THE METHOD
•The method is widely accepted as a screening
procedure and has been modified by many
investigators.
•Chlordiazepoxide (20mg/kg i.p.), diphenylhydantoin
10mg/kg i.p.) and phenobarbitone sodium (20mg/kg
i.p.) were found to be effective.

10. •Predominantly, the muscle relaxant and
anticonvulsant effects of benzodiazepines are
measured by this test.
•Stimulant, anti-depressant, neuroleptic and some
anti-epileptic drugs do not show MTZ-antagonism at
tolerable doses (Lippa et al. 1979).

11. •Nevertheless, the antagonism of MTZ induced seizures
appears to be a suitable procedure for detecting
compounds with potential anxiolytic activity.
•Among a battery of tests, the MTZ-antagonismhas been
proposed to study centrally acting skeletal muscle
relaxants (Bastian et al. 1959; Domino 1964).

12. 2. STRYCHNINE-INDUCED
CONVULSIONS PURPOSE AND
RATIONALE

13. •The convulsing action of strychnine is due to
interference with postsynaptic inhibition mediated by
glycine.
•Glycine is an important inhibitory transmitter to
motoneurons and interneurons in the spinal cord,
•Strychnine acts as a selective, competitive antagonist to
block the inhibitory effects of glycine at all glycine
receptors.

14. •Strychnine-sensitive postsynaptic inhibition in
higher centers of the CNS is also mediated by
glycine.
•Compounds which reverse the action of
strychnine have been shown to have anxiolytic
properties.

15. PROCEDURE
•Groups of 10 mice of either sex with a weight
between 18 and 22g are used.
•They are treated orally with the test compoundor the
standard (e.g. diazepam 5mg/kg).
•One hour later the mice are injected with 2mg/kg
strychnine nitrate i.p.

16. •With this dose of strychnine convulsions are
observed in 80% of the controls.
•The time until occurrence of tonic extensor
convulsions and death is noted during a 1h
period.
•With this dose of strychnine convulsions are
observed in 80% of the controls.

17. EVALUATION
• ED50-values are calculated using various
doses taking the percentage of the controls
as 100%.
•For time response curves the interval
between treatment and strychnine injection
varies from 30 to 120min.

18. CRITICAL ASSESSMENT OF THE
METHOD
• The method has been proven to be useful in
a battery of tests to characterize CNS-active
drugs. (Costa et al. 1975).

19. PICROTOXIN INDUCED
CONVULSIONS

20. •Picrotoxin induced convulsions are used to
further evaluate CNS-active compounds.
•Picrotoxin is regarded as a GABAA-antagonist
modifying the function of the chloride ion
channel of the GABAA receptor complex.

21. PROCEDURE
• Groups of 10 mice of either sex with a weight between
18 and 22g are treated either orally or i.p. with the test
compound or the standard (e.g. 10mg/kg diazepam
i.p.).
• 30 Mins after i.p. treatment or 60min after oral the
animals are injected with 3.5mg/kg s.c. picrotoxin

22. Observed for the following symptoms during the next
30min:
• Clonic seizures,
• Tonic seizures,
• Death.
• Times of onset of seizures
• Time to death

23. EVALUATION
•For time-response curves the animals receive the drug
30, 60 or 120min prior to picrotoxin.
•Protection is expressed as percent inhibition relative
to vehicle control.
•The time period with the greatest percent inhibition is
said to be the peak time of drug activity.
•ED50-values are calculated taking the percentage of
seizures in the control group as 100%.

24. CRITICAL ASSESSMENT OF THE
METHOD
• The method has been proven to be of value
amongst a battery of tests for CNS-activity.

25. MODIFICATIONS OF THE METHOD
• Buckett (1981) describes an intravenous bicuculline
test in mice.
•The compound bicuculline antagonizes the action of
GABA by competition on postsynaptic receptors.

26. • In the whole animal bicuculline reproducibly
induces myoclonic seizures.
• An intravenous dose of 0.55mg/kg was found to
induce myoclonic seizures in 90–100% of mice with
less than 10% mortality.

27. ISONIAZID-INDUCED
CONVULSIONS

28. •Isoniazid can precipitate convulsions in patients
with seizure disorders.
•The compound is regarded as a GABA-synthesis
inhibitor (Costa et al. 1975).
•Clonic-tonic seizures are elicited in mice which
are antagonized by anxiolytic drugs.

29. PROCEDURE
• Ten mice of either sex with a weight of 18 to 22g
are treated with the test compound or the
standard (e.g. diazepam 10mg/kg i.p.) by oral or
intraperitoneal administration.
• Controls receive the vehicle only.

30. •30min after i.p. or 60min after p.o. treatment the
animals are injected with a subcutaneous dose of
300mg/kg isoniazid (isonicotinic acid hydrazide).
•During the next 120min the occurrence of clonic
seizures, tonic seizures and death is recorded.

31. EVALUATION
• The percentage of seizures or death occurring in
the control group is taken as 100%.
•The suppression of these effects in the treated
groups is calculated as percentage of controls.
• ED50-values are calculated.

32. • The method has been proven to be of value
amongst a battery of tests for CNS-activity.
CRITICAL
ASSESSMENTOFTHEMETHOD

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