(A) Left In vivo whole-cell recordings were made from CA1 pyramidal neurons. The TBS was applied through the patch pipette. Right An example of TBS. EPSP-like waveforms were applied in bursts of 10 (at 100Hz, inset), these bursts were repeated 10 times at theta frequency (5Hz) and the process was repeated three times with an interval of 15 seconds. (B) Morphology of a recorded cell. SR stratum radiatum, SP stratum pyramidale, SO stratum oriens. (C-D) Examples of a TBS and a control cell. The plots show the response to each of the maximum current injections at different times during the testing protocol (grey circles). The red circles mark the mean response at each timepoint. The traces shown in (D) are marked by dark grey borders at their respective timepoints. (E) Left Mean number of spikes evoked in response to the maximal current injection prior to and 20 minutes post-TBS for each cell. Right Distribution of changes in spike count (F) Comparison of change in firing rate at 20 minutes between TBS and control groups. (G) Correlation between the number of spikes evoked during TBS and the change in firing rate. (H) Firing rate vs injected current for the populations of TBS and control cells. The current range is normalized to correct for differences in the range of current amplitudes used. In the TBS group there was a significant reduction (p < 0.05) in the intercept at 10 min (green) and 20 min (red) post-TBS but no change in the gain of the fits. Error bars show mean ± SEM. TBS n = 16 (30 min n = 14), Control n = 11 (30 min n = 6).