Initial studies with slices from BAF53bΔHDlow did not detect any abnormalities in the LTP elicited by ten theta bursts from that obtained in wildtype cases (Fig 5B). We therefore repeated the experiment using trains of five theta bursts, a protocol that is closer to the threshold for eliciting stable LTP in mice. A pronounced defect was found under these conditions. Five bursts delivered to wildtype slices produced STP and LTP effects comparable to those induced by ten bursts; slices from the BAF53bΔHDlow exhibited normal STP but potentiation failed to stabilize and over the next hour decayed to levels that were markedly lower than those recorded for the controls (p<0.001 at 50-60 min post TBS; Fig 5C). We conclude from these results that low expression of the BAF53bΔHD mutant is sufficient to markedly impair the machinery required to consolidate LTP and that this impairment can be overcome by supra-threshold stimulation.
