Involvement of hippocampal CA3 KATP channels in contextual memory

This paper evaluates the involvement of hippocampal ATP-sensitive potassium channels (K_ATP) in learning and memory. After confirming expression of the Kir6.2 subunit in the CA3 region of C57BL/6J mice, we performed intra-hippocampal pharmacological injections of specific openers and blockers of K_ATP channels. The opener diazoxide, the blocker tolbutamide, or a mixture of both, were bilaterally injected in the CA3 region before we subjected the animals to a fear conditioning paradigm. Diazoxide strongly impaired contextual memory of mice at both doses tested. This impairment was specifically reversed by co-injecting the blocker tolbutamide. Moreover, we studied the mnemonic abilities of mice deleted for the Kir6.2 subunit. These mice were backcrossed to C57BL/6J mice and tested in two learning paradigms. We found a significant impairment of contextual and tone memories in the Kir6.2 knock-out mice when compared with heterozygous or wild-type animals. Furthermore, these animals were also slightly impaired in a spatial version of the Morris water maze task. Our data suggest a specific involvement of hippocampal K_ATP Kir6.2/SUR1 channels in memory processes.