RESUMO
A number of convulsant drugs were found to improve memory function though in doses that would be hazardous to humans. [-]-beta-Hydrastine; a less hazardous convulsant, was investigated for potential antiamnestic properties by testing its effect on retention memory of an inhibitory avoidance task in mice. [-]-beta-Hydrastine was found to enhance memory function where one training session was enough for the animals to learn the task only when 0.025, 0.05, 0.1, or 0.2 mg/kg of the drug was injected immediately after training. Midazolam [1mg/kg] intraperitoneally administered 30-mm before or immediately after a two-session training induced anterograde and retrograde amnesia respectively. [-]-beta Hydrastine was able to block midazolam-induced anterograde amnesia, where 0.05 and 0.1 mg/kg of hydrastine injected immediately after, rather than before, training were enough to increase the step-down latency in the test session. Furthermore, 0.1 mg/kg of [-]-beta-hydrastine enhanced acquisition and retrieval memory. These effects were shown not to be due to hyperalgesic or motoric qualities respectively, though the effect of [-]-beta-hydrastine on acquisition was reversed with pretest adminstration of the drug. The antiamnestic dose of [-]-beta-hydrastine was 1/398 its convulsive dose 50%. In conclusion, this work showed [-]-beta-hydrastine to be a much less hazardous antiamnestic drug than the rest of its class of brain stimulants. It also suggests the involvement of benzodiazepine system in the antiamnestic properties of [-]-beta-hydrastine with enhanced receptor sensitivity following acute stress