PROTECTIVE EFFECT OF UNDER-REINFORCEMENT OF PASSIVE-AVOIDANCE AGAINSTSCOPOLAMINE-INDUCED AMNESIA

Administration of antimuscarinic drugs induces amnesia of aversively m otivated behaviors. However, when relatively high intensities of foots hock are used during training (over-reinforcement), animals become pro tected against such amnesic state. Moreover, the protective effect is established in a none-or-all fashion, i.e., within a series of increas ing intensities a minute augmentation of footshock intensity is suffic ient to reach the protective threshold. In the present experiment it w as found that very low intensities of aversive stimulation (under-rein forcement), sufficient to produce learning, also protected animals fro m scopolamine-induced amnesia. These results suggest that acetylcholin e is critically involved in memory consolidation of passive avoidance, but only within a limited range of training intensities.