Contextual memory deficits observed in mice overexpressing small conductance Ca²⁺-activated K⁺ type 2 (K_Ca2.2, SK2) channels are caused by an encoding deficit

Hippocampal-dependent synaptic plasticity and memory are modulated by apamin-sensitive small conductance Ca²⁺-activated K⁺ (SK) channels. Transgenic mice overexpressing SK2 channels (SK2+/T mice) exhibit marked deficits in hippocampal memory and synaptic plasticity, as previously reported. Here, we examined whether SK2 overexpression affects the encoding or retention of contextual memory. Compared with wild-type littermates, SK2+/T mice exhibited significantly less context-dependent freezing 10 min and 24 h after conditioning. Interestingly, this contextual memory impairment was eliminated if SK2+/T mice were permitted longer pre-exposure to the conditioning chamber. These data support converging evidence that SK2 channels restrict the encoding of hippocampal memory.