Long-term Consumption of Capsicum annum (Chili Pepper) and Capsaicin Diets Impairs Visuo-Spatial Learning and Memory in CD-1 Mice

Background: Capsaicin annum (Chili pepper) is among the most consumed spices throughout the world. These spices/fruits contain chemicals called capsaicinoids. Capsaicin, the active principle in chilies is a major capsaicinoid responsible for up to 90% of the total pungency of pepper fruits. It is a generally known neurogenic, neurotoxic and analgesic agent. Since capsaicin is neurotoxic and has tendency to chemically interact with neurons, it may affect learning and memory.

Aim: It was therefore, the aim of this present study to investigate the effects of long-term consumption of capsaicin diet on learning and memory with a view of comparing them with those of chili pepper to see whether the effects of chili pepper on learning and memory can be attributed to capsaicin using adult CD-1 Swiss white mice as experimental animals.

Materials and Methods: Thirty male (30) mice were randomly assigned into three groups of ten mice each, namely; control, pepper-diet (20% w/w) and capsaicin-diet (10%w/w) groups. Feeding lasted for 28 days, during which there were daily measurements of food intake, water intake and body weight changes. Thereafter, their learning and memory abilities were assessed through their ability to locate the hidden platform model of Morris water maze apparatus.

Results: Pepper consumption reduced food intake but increased water intake in mice. The swim latencies of both capsaicin and pepper diet groups were significantly longer compared to control (p<0.001). The probe trial of the Morris water maze test showed a significantly shorter quadrant duration in the pepper and capsaicin groups compared to control (p<0.001 and p<0.01 respectively).

Conclusion: Long-term consumption of chili pepper and capsaicin diets impairs visuo-spatial learning and memory in mice.