Subchronic Crude Khat (<i>Catha edulis</i> F.) Extract Administration Produces Short-term Memory Impairment in Behavioral Tasks without Morphological Toxicity to the Dentate Gyrus in Mice

Abstract

People chew khat (Catha edulis F.), believing that it improves memory, alertness and clear thinking. Although such belief are widely held, there are little or no reports assessing the effect of khat on learning and memory as well as neural processes involved in these activities. The aim of the present study was therefore to evaluate the effect of acute, subacute, and subchronic exposure to crude khat extract on learning and memory using a host of behavioral paradigms followed by morphometric analysis in mice. To this effect, mice were orally administered with either vehicle (2% Tween 80 in water) or various doses of khat extract (100 mg/kg, 200 mg/kg, 300 mg/kg) and subjected to learning and memory tasks in Morris water maze (MWM), Multiple-T-maze (MTM) and/or active avoidance. In parallel, mice were administered with khat at doses of 100, 200 and 400 mg/kg for two months and subjected to morphometric analysis to determine different parameters. Acute and subacute exposure to khat had no effect on learning and memory in all behavioral tasks. Subchronic exposure, however, produced a significant impairment in short-term memory, without altering learning and long-term memory in MTM and MWM tasks. Morphometric analysis revealed a significant reduction in weight of brain as well as prosencephalon of khat treated animals compared to controls. This loss in weight, however, was not accompanied by any changes in the geometric properties of the dentate granule cells, including volume of the granular layer of the dentate gyrus as well as numerical density, total number, and diameter of the granular cells. The data collectively indicate that subchronic exposure to khat differentially alters short-term memory without any apparent morphological toxicity in neural processes underlying learning and memory. The weight loss observed could be attributed to other effects, such as anorexic and vasoconstrictive effects of khat.

Keywords: Catha edulis, dentate granular cells, active avoidance, water maze, multiple-T-maze