FIG 5.

Loss of paired-pulse inhibition and enhanced LTP in DREAM mutant mice. (A) For paired-pulse studies, the amplitude of the population spike evoked by the second stimulus, normalized to the amplitude of the population spike evoked by the first stimulus, is plotted as a function of the interstimulus interval for transgenic (tg, n = 6) and corresponding wild-type littermates (wt, n = 11). Note the complete suppression of the second population spike at short intervals in wild-type mice and its absence at all intervals in transgenic mice. Stimulus intensity was set so that the first stimulus of the pair evoked a population spike of ∼1 mV. Representative responses to paired stimuli for each group are displayed on the right. Calibration, 3 mV, 4 ms. (B) LTP was measured at perforant path-granule cell synapses in anesthetized transgenic and wild-type mice. LTP, measured 50 to 60 min after the tetanus (arrow), was significantly enhanced. The magnitude of LTP was 32.3% ± 2.6% for transgenic and 13.7% ± 4.0% for wild-type mice (P < 0.005).