Effects of phenobarbital on SPWs. A. SPW-R complexes recorded from a slice bathed in normal medium and under consequently increasing concentrations of phenobarbital (a) showing that the rate of spontaneous activity was increased at 50 and 100 μM and reduced at 200 and 400 μM (asterisk denotes the lowest drug concentration with statistical significance effect, paired t-test, P < 0.001 paired t t-test, P < 0.05). In the plot of instantaneous period (b) note that even at the highest concentration (400 μM) phenobarbital did not abolish spontaneous activity. Measures for constructing the plot of collective data (c) were obtained from 3, 6, 10, 12 and 18 slices respectively for the five drug concentrations. B. Example of auto-correlation analysis for SPWs recorded in one slice before and during application of 100 μM of phenobarbital (diagram on the left). The collective data plot (diagram on the right) illustrates that only at 400 μM did the drug significantly reduce rhythmicity of SPWs (asterisk, P < 0.05). Data were obtained from 6, 10, 10 and 12 slices respectively for the four drug concentrations. C. Averages of filtered SPWs recorded from an epoch lasting two minutes (a) obtained from a slice bathed in normal medium (trace with the smallest amplitude) and increasing concentrations of phenobarbital (50, 200 and 400 μM, traces with consecutively increasing amplitude). Note the concomitant increase in the falling phase and the amplitude of the potentials. The drug significantly increased half-width of SPWs at the highest concentration of 400 μM (b). However, the drug did not significantly change the amplitude of SPWs at any concentration (c). Data in collective plots were obtained from 6, 10, 12 and 18 slices respectively for the four drug concentrations in half-width and from 3, 6, 10, 12 and 18 slices for the five concentrations in amplitude. D. Phenobarbital significantly decreased synchronization only at 400 μM, as illustrated in the example (on the left) and collective diagram (on the right, paired t-test, P < 0.05). The concentration of 25 μM is missing from the plots of auto-correlation, half-width and cross-correlation because measures of these variables were obtained from only one experiment.