Effect of 20(S)-ginsenoside-Rg2 and cyproheptadine on two-way active avoidance learning and memory in rats.

The effects of 20(S)-ginsenoside-Rg2 (GRg2, CAS 52286-74-5) and cyproheptadine (CYP, CAS 129-03-3) on acquisition, retention and retrieval were examined in male Wistar rats using a two-way active avoidance method. Learning and memory were estimated by the avoidance rate (%) and/or latency (s). Acute administration of CYP 1.0 mg/kg i.p. 30 min prior to training produced a significant impairment in acquisition of 3 d learning and 48 h memory by decreasing the rate from 87.9 +/- 2.1, 75.8 +/- 4.9 in saline rats to 55.8 +/- 9.6, 53.4 +/- 8.4, respectively (F(1,14) = 10.7, 14.8, p < 0.01). The CYP administration immediately following the end of training and 30 min before testing produced the impairments in retention of 24 h memory and in retrieval of 48 h memory by decreasing the rate from 86.7 +/- 1.7, 93.3 +/- 2.7 to 55.0 +/- 5.5, 60.0 +/- 6.8, respectively (F(1,12) = 27.2, 10.5, p < 0.01). Repeated administration of GRg2 20 mg/kg i.p. significantly improved the CYP-induced recognitional deficits by increasing the CYP-decreased rate from 55.8 +/- 9.6 to 80.8 +/- 4.2 in d 3 learning acquisition (F(1,14) = 5.6, p < 0.05), from 53.4 +/- 8.4 to 60.0 +/- 8.2 in 48 h memory acquisition (F(1,14) = 7.5, p < 0.05) and from 55.0 +/- 5.5 to 88.3 +/- 2.5 in 24 h memory retention (F(1,12) 27.5, p < 0.01) as well as from 60.0 +/- 6.8 to 85.6 +/- 6.9 in 48 h memory retrieval (F(1,12) = 5.2, p < 0.05), respectively. The results also provide the suggestive evidence that central serotonin may play a positive modulatory role in the acquisition, retention and retrieval of two-way active avoidance responding in rats.