Effect of apamin, a toxin that inhibits Ca(2+)-dependent K+ channels, on learning and memory processes.

Apamin, a neurotoxin extracted from bee venom, specifically binds to a particular class of Ca(2+)-activated K+ channels which are involved in the slow afterhyperpolarization (S-AHP) that follows action potentials in many excitable cells. We tested in mice the effects of apamin on learning and memory processes. The results showed that pre-training injection of apamin accelerated the acquisition of a bar-pressing response but also increased the bar-pressing rates of the animals. This latter result suggests that apamin accelerated acquisition because it increased behavioral activity in general and the number of bar-presses in particular. Post-training apamin injection retroactively and non-contingently facilitated memory processes taking place shortly after training in a bar-pressing task. The lack of an effect of the delayed apamin injection showed that apamin did not act proactively on memory retrieval processes. These results suggest that apamin-sensitive KCa channels may contribute to memory processes.