Effects of thiopental on Sharp Waves. A. Example of field recordings (a) and plot of instantaneous period (b) illustrating that thiopental induced a concentration-dependent and reversible increase in the inter-event period. Horizontal bars in "b" denote the time of application of consecutively larger drug concentrations. Relatively large data values of period during 100 and 200 μM of the drug are curtailed for reasons of clarity of lower values. Note the great value dispersion of instant period during drug application at ≥50 μM. Data in "a" and "b" were obtained from two different slices. The collective data plot (percent changes) of period is shown in (c). The asterisk here, as in the subsequent collective plots in the figure, denotes the lowest concentration with statistically significant drug action (paired t-test, P < 0.001 at 50 μM and P < 0.05 at 100–200 μM). The number of slices studied at the five concentrations, of 10, 25, 50, 100 and 200 μM, were respectively 12, 18, 22, 12 and 8. Error bars not shown were smaller than the size of the symbol. B. Example of auto-correlation before and during 50 μM thiopental (a) and collective auto-correlation plot (b) showing the disruption of rhythmicity at concentrations ≥25 μM (paired t-test, P < 0.05 at 25 μM and P < 0.01 at ≥50 μM). Numbers of slices studied at the five concentrations were 5, 6, 12, 8 and 4. C. Example of thiopental-induced prolongation of SPWs (a) at two different concentrations. Averages of low-pass filtered sweeps taken from a two minute epoch are shown. Dotted traces are control sweeps. The corresponding collective plot (b) shows that significant prolongation of single SPWs occurred at drug concentrations ≥50 μM (paired t-test, P < 0.01). D. Effect of thiopental on SPWs' synchronization along the CA1 region. Single SPWs simultaneously recorded from two locations along the CA1 st. pyramidale, measuring 1 mm, are shown in "a", before (traces on the left) and during application of 50 μM thiopental (traces on the right). Sweeps were low-pass filtered in order to make feasible the time-discrimination of their peaks. Note the increased phase-lag (marked by dotted lines) during drug application (9.25 ms) compared with control condition (3.8 ms). The cross-correlation plot from another slice (b) illustrates the large decrease of function value during drug application at 100 μM. The collective plot (c) shows that significant suppression of synchrony started at 25 μM and reached a plateau at 100 μM (P < 0.05 at 50 μM and P < 0.01 at ≥50 μM). Numbers of slices studied at the five concentrations were 3, 5, 5, 4 and 4.