The nootropic properties of ginseng saponin Rb1 are linked to effects on anxiety

Previous studies have shown that crude ginseng extracts enhance performance on shock-motivated tasks. Whether such performance enhancements are due to memory-enhancing (nootropic) properties of ginseng, or,to other non-specific effects such as an influence on anxiety has not been determined. In the present study, we evaluated both the nootropic and anxiolytic effects of the ginseng saponin Rb-1. In the first experiment, 80 five-day-old male chicks received intraperitoneal injections of 0, 0.25, 2.5 or 5.0 mg/kg Rb-1. Performance on a visual discrimination task was evaluated 15 minutes', 24 and 72 hours later. Acquisition of a visual discrimination task was unaffected by drug treatment, but the number of errors was significantly reduced in the 0.25 mg/kg group during retention trials completed 24 and 72 hours after injection. Animals receiving higher dosages showed trends towards enhancement initially, but demonstrated impaired performance when tested 72 hours later. Rb-1 had no effect on response rates or body weight. In the second experiment, 64 five-day-old male chicks received similar injections of Rb-1 (0, 0.25, 2.5 or 5.0 mg/kg) and separation distress was evaluated 15 minutes, 24 and 72 hours later. Rb-1 produced a change in separation distress that depended on the dose and environmental condition under which distress was recorded. These data suggest that Rb-1 can improve memory for a visual discrimination task and that the nootropic effect may be related to changes in anxiety.