Background

Khat (Catha edulis (Vahl) Forssk Ex. Endal) chewing for its social reasons and euphoric effect is a common practice in khat growing countries. Khat chewing is known to affect the gastrointestinal motility, but no sufficient study has been conducted to address its effect and the mechanism of action. This study assessed the effect of khat on the mouse gastrointestinal motility and suggested the pharmacological basis for the effect.

Materials and Methods

For in vivo study, a crude extract of khat (100 mg/kg, 200 mg/kg and 400 mg/kg) was feed to the mice and the gastrointestinal transit time (GITT), glass bead expulsion time and distance of the charcoal suspension traveled through the small intestine was recorded and compared to the control. For in vitro study, isolated mice colon segment preparations were used to assess the effect of khat on the contractile response and to suggest the mechanism of action.

Results

In vivo experiments result showed that, feeding khat extract (100 mg/kg, 200 mg/kg and 400 mg/kg) inhibited mouse gastrointestinal motility. Khat extract increased GITT (P < 0.01), prolonged the glass bead expulsion time (P < 0.05) and decreased the distance the charcoal meal travelled through the small intestine significantly. In vitro study results also showed that khat extract (0.05 – 1 mg/ml) significantly decreased the contractile response of the mice colon concentration-dependently. Atropine (10 µM) and verapamil (0.01 – 0.1 µM) also have inhibitory effect on the mice colon segment contractility.  The same as verapamil (0.01 – 0.1μM), khat extract (0.05 – 0.5 mg/ml)  inhibited high K⁺-induced sustained contraction and shifted the Ca²⁺ concentration response curve towards the right.

Conclusions

The crude extract of khat evoked an inhibitory effect on mouse gastrointestinal motility and spasmolytic effect on the colon. The spasmolytic effect was mediated through blocking the voltage dependent Ca²⁺ channels.