Aqueous methylcellulose

Gastrointestinal propulsion of a charcoal meal was measured according as described by Sagar et al. [49 (link)] with slight modifications. Test animals were fasted 18 h prior to the experiment. Ten minutes after the last dose of the test compound (sixth day of administration), the animals from each group were fed 1 ml of a charcoal meal containing 3% suspension of activated charcoal in 0.5% aqueous methylcellulose (Sigma-Aldrich Co. Ltd., St. Louise, MO, USA). Thirty minutes after administration of the charcoal meal, 99.0% CO₂ gas as a euthanasia agent was used, for euthanasia of rodents [50 (link)] and the animals were sacrificed via cervical dislocation. The intestinal charcoal transit ratio was estimated following the Eq. 3. $$\text{Charcoal transit ratio}\left(\%\right)=\left[\left(\text{total small intestine length}-\text{charcoal meal transfer length}\right)/\text{total small intestine length}\right]\times 100$$

The assessment of gastrointestinal propulsion of the charcoal meal was determined according to Sagar et al. [40 ] with minor modifications. Test animals were starved for 18 h prior to the experiment but were allowed access to water ad libitum. Ten minutes after the sixth (final) administration of the test agent, animals from each group were fed 1 mL charcoal meal (3% activated charcoal suspension in 0.5% aqueous methylcellulose (Sigma, MO, USA)). Thirty minutes after administration of the charcoal meal, the animals from each group were euthanized by cervical dislocation, and the total intestinal length (pyloric sphincter to caecum), as well as the charcoal transit distance as a fraction of that length, was measured. The intestinal charcoal transit ratio was calculated as the difference between the total small intestinal length and the charcoal meal transit distance as follows: charcoal transit ratio (%) = ((total small intestinal length − charcoal meal transit distance)/total small intestinal length) × 100.