Drug disruption of short-term memory in Drosophila melanogaster.

Recent work on operant visual learning and memory in Drosophila has suggested at least three distinct memory phases. Trying to disrupt memory pharmacologically, we fed flies with ouabain or the depolarizing drugs potassium chloride (KCl), lithium chloride (LiCl) and monosodium glutamate for some specific time before training. The depolarizing drugs abolished memory very soon after training. Ouabain exerted no effect on memory within the first 20 min but abolished it more than 30 min after training. These drugs had no diminishing effects on the visual discrimination and behavioral performance of the flies during training. This result suggests that memory disruption may not be induced by nonspecific effects of the drugs. In addition, reversal training of the KCl-fed flies indicates that KCl appears not to impair the retrieval mechanism of flies. These results suggest that the specific disruptive effects of the drugs on memory formation and the existence of a short-term memory phase, are susceptible to disruption of the depolarizing drugs but unaffected by ouabain.