Gastrodia elata Bl. Attenuated Learning Deficits Induced by Forced- Swimming Stress in the Inhibitory Avoidance Task and Morris Water Maze

This study adopted the forced-swimming paradigm to induce depressive symptoms in rats and evaluated the effects on learning and memory processing. Furthermore, the effects of the water extract of Gastrodia elata Bl., a well-known Chinese traditional medicine, on amnesia in rats subjected to the forced-swimming procedure were studied. Rats were subjected to the forced-swimming procedure, and the inhibitory avoidance task and Morris water maze were used to assess learning and memory performance. The acquisition of the two tasks was mostly impaired after the 15-minute forced-swimming procedure. Administration of the water extract of G. elata Bl. for 21 consecutive days at a dosage of 0.5 or 1.0 g/kg of body weight significantly improved retention in the inhibitory avoidance test, and the lower dose showed a better effect than the higher one and the antidepressant fluoxetine (18 mg/kg of body weight). In the Morris water maze, the lower dose of the water extract of G. elata Bl. significantly improved retention by shortening escape latency in the first test session and increasing the time in searching the target zone during the probe test. These findings suggest that water extracts of G. elata Bl. ameliorate the learning and memory deficits induced by forced swimming.