AIM: Anticonvulsant activity assessment using Maximal Electroshock Method (MES) in rats
REFERENCE:
1) M.N. Gosh Common Laboratory Animals, Fundamentals of Experimental Pharmacology, Fifth Edition, 2011
2) Kulkarni S.K., Handbook of experimental pharmacology, New Delhi: Vallabh Prakashan, 2014.
INTRODUCTION
Epilepsy, a complex neurological condition characterized by recurrent seizures, affects millions worldwide. To explore potential treatments, researchers turn to animal models that replicate seizure activity. Among these models, the maximal electroshock (MES) method stands out. By inducing convulsions in laboratory rats, MES mirrors the tonic-colonic phases observed in human epilepsy. In our study, we narrow our focus to phenytoin, a widely used antiepileptic drug. Before embarking on this investigation, a solid grasp of antiepileptic pharmacology is essential. Let’s delve into the intricacies of this experiment.
REQUIREMENTS:
Apparatus: Electro-convulsometer, corneal electrode (apply 150 mA current for 0.2 sec), stopwatch
Animal: Rat (150-200 gm)
Drugs: phenytoin (Dose 25 mg/kg; prepare a stock solution containing 5 mg/ml of drug and inject 0.5 ml/100g body weight of the animal).
PRINCIPLE:
· Maximal Electroshock (MES): This method simulates grand mal epilepsy in animals.
· MES Convulsions Phases:
1. Tonic Flexion: Initial phase with muscle stiffness.
2. Tonic Extensor: Follows tonic flexion, characterized by extension of limbs.
3. Clonic Convulsion: Repetitive muscle contractions.
4. Stupor: A period of altered consciousness.
5. Recovery or Death: Outcome after convulsions.
· Anticonvulsant Activity Assessment:
1. A substance is considered anticonvulsant if it reduces or abolishes the tonic extensor phase of MES convulsions.
2. Phenytoin is a known antiepileptic drug.
OBSERVATION TABLE:
Control group
SR. NO.
Body weight (g)
Treatment
Time (sec) in various phases of convulsion
Flexion
Extensor
Clonus
Stupor
Recovery / death
1
Control
2
3
4
5
6
Mean
Test group
Phenytoin
INFERENCE:
150
15
127
Recovery
165
13
119
156
14
124
180
12
115
195
9
110
170
117
4.3
12.6
4.6
118.6
155
60
58
175
52
185
48
45
56
2.6
3.16
2.3
53.16
*Observation table after completion of the experiment can be downloaded by clicking tab (RJPT SimLab)
DISCLAIMER: "The results provided here are only for reference or comparison purposes. Students are expected to perform the experiment and record their actual observations."
GRAPH:
PROCEDURE:
1. Animal Preparation and Grouping:
o Weigh and number the rats.
o Divide them into two groups, each consisting of 6 rats:
§ Control Group: This group will not receive any drug treatment.
§ Test Group (Phenytoin): This group will receive phenytoin as the antiepileptic drug.
2. Electroshock Application and Observation:
o Properly hold the rat and place corneal electrodes on the cornea.
o Apply the prescribed current to induce maximal electroshock (MES).
o Note the different stages of convulsions:
§ Tonic Flexion: Initial muscle stiffness.
§ Tonic Extensor Phase: Extension of limbs.
§ Clonic Convulsions: Repetitive muscle contractions.
§ Stupor: Altered consciousness.
§ Recovery or Death: Outcome after convulsions.
o Record the time (in seconds) spent by the animal in each phase.
o Repeat the procedure with other animals in the control group after inducing the Drug.
3. Phenytoin Administration:
o Inject phenytoin intraperitoneally (I.P.) to a group of 6 rats in the test group.
o Wait for 30 minutes to allow phenytoin to take effect.
4. Repeat Electro-Convulsions:
o Subject the animals in the test group to electro-convulsions as described in step 2.
o Observe any reduction in the duration of the tonic extensor phase of MES-induced convulsions.
o Document any abolition of the tonic extensor phase due to phenytoin treatment.
RESULTS:
1. Control Group:
o Rats subjected to maximal electroshock (MES) without any drug intervention.
o Observed MES-induced convulsions, including tonic flexion, tonic extensor, clonus convulsion, stupor, and recovery or death.
2. Drug Treatment Group (Phenytoin):
o Administered phenytoin intraperitoneally (I.P.) to rats.
o Noted the effect on MES-induced convulsions.
o Observations:
§ Reduced Tonic Extensor Phase: Phenytoin significantly reduced the duration of the tonic extensor phase.
§ Anticonvulsant Activity: Phenytoin demonstrated anticonvulsant properties by suppressing the most severe phase of convulsions.
3. Comparison:
o Compared results between control and drug treatment groups.
o Phenytoin’s efficacy in reducing MES-induced convulsions validates its antiepileptic potential.
CONCLUSION:
o Phenytoin holds promise as an effective antiepileptic agent.
o Further studies are warranted to explore its mechanisms of action and safety profile.
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