Indian Journal of Pharmacology Medknow Publications on behalf of Indian Pharmacological Society ISSN: 0253-7613 EISSN: 1998-3751 Vol. 37, Num. 2, 2005, pp. 116-119

Indian Journal of Pharmacology, Vol. 37, No. 2, March-April, 2005, pp. 116-119

Research Paper

Skeletal muscle relaxant effect of Chonemorpha macrophylla in experimental animals

Roy Ranendra Kumar, Ray N.M., Das A.K.

Department of Pharmacology, N.R.S. Medical College, Kolkata - 700 014

Correspondence Address:Department of Pharmacology, N.R.S. Medical College, Kolkata - 700 014
E-mail: rayon@vsnl.net / rkroy_08@rediffmail.com

Code Number: ph05021

ABSTRACT

INTRODUCTION

Preparation of the alcoholic extract of CM

Powdered bark of CM (1.5 kg) was saxhleted with petroleum ether (B.P. 60-80 ºC) for 24 h. The solvent was distilled off on water bath leaving a gummy residue (17 g). The defatted plant material was dried up in air and was percolated with ammonia and rectified spirit for 21 days. The solvent was removed under reduced pressure when a gummy residue (10 g) was obtained. This alcoholic extract was soluble in propylene glycol on little warming. A stock solution of 1 g of alcoholic extract of CM was prepared in 20 ml of propylene glycol to make the concentration 50 mg/ml and was utilized for different experiments as mentioned below.

The effect of the drug was first studied on isolated frog rectus abdominis muscle by adopting standard procedure.[3] A portion of frog rectus abdominis muscle was mounted in frog ringer solution in 5ml capacity organ bath maintained at 37±0.5 ºC and aerated with oxygen. Each preparation was allowed to equilibrate for 30 min under the resting tension of 1 g to obtain stable basal condition.

Initially, a concentration of acetylcholine (2.5 x 10^-7 M) was identified which can produce sub maximal contraction (3.02 cm) of the muscle. Contact time was 90 seconds. The effect of the vehicle propylene glycol (0.1 ml) was noted by adding the vehicle in the bath and allowing to remain in contact with the muscle for 3 min followed by addition of the dose of acetylcholine. Any change in height was recorded. Similarly, the effects of the alcoholic extract of CM (2 mg/ml), succinylcholine (1.25 x 10^-7 M) and gallamine (2.5 x 10^-7 M) on acetylcholine-induced contractions were recorded. To know the effect of physostigmine (3.3 x 10^-6 M) and potassium chloride (3 x 10^-1 M) on the antiacetylcholine effect of the alcoholic extract of CM, the respective agent was first administered into the bath 90 sec before administration of the alcoholic extract of CM. Three minutes after administration of the test drug the preparation was then challenged with the same dose of acetylcholine.

Similarly, the effects of physostigmine and potassium chloride on the antiacetylcholine effect of succinylcholine and gallamine were studied and compared with the test drug.

Then the effect of the alcoholic extract of CM on isolated rat phrenic nerve diaphragm preparation was carried out by the method of Bulbring.[4] A triangular flap of diaphragm muscle was cut out with a portion of phrenic nerve attached to it from an albino rat weighing about 200 g. The muscle was mounted in a large organ bath containing 40 ml of Krebs solution maintained at 37.0±0.5 ºC and aerated with oxygen. The preparation was allowed to equilibrate for 45 min under resting tension of 1-2 g. Contact time for each agent was 3 min.

The preparation was stimulated indirectly (2V) through the phrenic nerve with supramaximal square wave pulse of 0.5 milliseconds duration at 0.5 Hz. The effects of the vehicle and the alcoholic extract of CM in the concentration of 50 and 100 µg/ml on electrically stimulated contraction of rat diaphragm were recorded.

To know whether physostigmine could modify the inhibitory effect of the test drug on electrically stimulated contraction of diaphragm, a dose of physostigmine (4 x 10^-5 M) was added to the bath following the administration of the test drug (100 µg/ml) and the effect was recorded for 5 min.

The type of skeletal muscle relaxation produced by CM was studied in unanaesthetized intact young chicks by the method of Battle and Zaimis.[5] The chicks weighing about 250 g were divided into 5 groups, each group containing 6 chicks. Each group of chicks received either propylene glycol (0.1 ml), alcoholic extract of CM (10 and 20 mg/kg), succinylcholine (0.05 mg/kg) or gallamine (0.05 mg/kg). All the drugs were administered i.v. through the wing vein of the chicks. The chicks of each group were observed carefully and any difference in the position of the limbs and neck were noted and compared.

Statistical analysis

Student′s ′t ′ test was used to evaluate the difference in the height of contraction. The onset and duration of the paralysis of different drugs were compared using one-way analysis of variance (ANOVA) followed by Dunnett′s test. A P value < 0.05 was considered significant.

RESULTS

Studies on isolated skeletal muscle preparation of frog rectus abdominis muscle reveals that the alcoholic extract of CM can antagonize acetylcholine-induced contraction of the preparation. Pretreatment with potassium chloride reverses the muscle relaxant effect of gallamine but not that of the test drug or succinylcholine. The observation suggests that the alcoholic extract of CM possesses a depolarizing type of neuromuscular blocking action. This is further substantiated by the observation that pretreatment with physostigmine, which antagonizes the inhibitory effect of gallamine, enhances the inhibitory effect of both the alcoholic extract of CM and succinylcholine.

On isolated rat phrenic nerve diaphragm preparation, the alcoholic extract of CM reduces nerve stimulation-induced contraction of diaphragm, which is potentiated by the addition of physostigmine. The observation lends further support to the fact that CM possesses depolarizing type of neuromuscular blocking action.

The effect of CM on intact animals like young chicks further elucidates its mechanism of action. The drug produces extension of the neck and limbs like succinylcholine, a depolarizing blocker, whereas gallamine, a non-depolarizing blocker, produces flaccid type of paralysis.

Thus it is concluded that the alcoholic extract of CM possesses a depolarizing type of skeletal muscle relaxant property. In other words, the drug resembles succinylcholine with a slower onset and shorter duration of action.

REFERENCES

Copyright 2005 - Indian Journal of Pharmacology

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