Evaluation of Antidiarrhoeal Agents

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Chapter: Pharmacognosy and Phytochemistry : Biological Screening of Herbal Drugs

The method followed here is the method of Awouters et al. (1978) with modification. The original method included only male wistar rats (220–250 g), where they were starved overnight before treatment with the selected drug in the next morning. In the present study, rats of either sex (180–200 g) are fasted for 18 hours. ....


EVALUATION OF ANTIDIARRHOEAL AGENTS

 

 

Castor Oil-Induced Diarrhoea in Rats

 

The method followed here is the method of Awouters et al. (1978) with modification. The original method included only male wistar rats (220–250 g), where they were starved overnight before treatment with the selected drug in the next morning. In the present study, rats of either sex (180–200 g) are fasted for 18 hours. Animals are housed in six in each. Varying doses of the test drugs are admin-istered orally by gavage as suspension to different groups of animals. The next group received dipehnoxylate (5 mg/ kg) orally as suspension as standard drug for comparison. Other group that served as control is treated with the control vehicle only.

 

One hour after treatment, each animal receives 1 ml of castor oil orally by gavage and then observed for defeca-tion. Up to 4th hour after the castor oil challenge, the presence of characteristic diarrhoeal droppings are noted in the transparent plastic dishes placed beneath the indi-vidual rat cages.

 

The effects of the test drug like the standard antidiar-rhoeal agent, diphenoxylate, are calculated based on the frequency of defecation when compared to untreated rats. Both substances also should reduce greatly the wetness of faecal droppings.

 

Gastrointestinal Motility Tests

 

Rats are fasted for 18 h and placed in different cages containing six in each. Each animal is administered orally with 1 ml of charcoal meal (3% deactivated charcoal in 10% aqueous tragacanth). Immediately after that the first few groups of animals are administered orally with the test drug at varying doses. Next group receives atropine (0.1 mg/kg, i.p), the standard drug for comparison. The last group is treated with aqueous tragacanth solution as control. Thirty minutes later, each animal is killed and the intestinal distance moved by the charcoal meal from the pylorus is cut and measured and expressed as a percent-age of the distance, the charcoal meal has moved from the pylorus to the caecum.

 

The antidiarrhoeal test drugs decrease propulsion of the charcoal meal through the gastrointestinal tract when compared with the control group by this model which is comparable to that of atropine (standard drug) which reduces the motility of the intestine significantly.

 

PGE2-Induced Enteropooling

 

In this method, rats of the same stock as above are deprived of food and water for 18 h and are placed in six perforated cages with six animals per cage. The first few groups of rats are treated with varying doses of the test drug. The last two groups are treated with 1 ml of 5% v/v ethanol in normal saline (i.p.). The last group of this is then treated with the control vehicle, which served as control. Immediately after-wards, PGE2 is administered orally to each rat (100 μg/kg) in 5% v/v ethanol in normal saline. After 30 minutes, each rat is killed and the whole length of the intestine from the pylorus to the caecum dissected out and its contents are collected in a test tube and the volume is measured.

 

PGE2 induces significant increase in the fluid volume of rat intestine when compared with control animals receiving only ethanol in normal saline and control vehicle. The antidiarrhoeal test drugs inhibit this PGE2-induced enteropooiing. Statistical analysis is performed by student’s ‘t’ test, and in all the cases results are expressed as mean ± SE.

 

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