Fig. 7.
Summary of effects of corticothalamic burst intensity and GABAA and GABAB antagonists.a, One corticothalamic stimulus per thalamic burst produces spontaneous 6–7 Hz spindle wave-like oscillations (leftmostbar inhistogram). As the number of stimuli in the 200 Hz burst is increased, the oscillation frequency gradually slows until it reaches 3–4 Hz at six stimuli per burst. Further increases in the number of stimuli do not produce large changes in oscillation frequency, possibly because GABAB receptors are maximally activated. Data are from the cell illustrated in Figures 4 and 5. The numbers of interstimulus intervals averaged to calculate oscillation frequencies for 1 through 10 stimuli were 54, 19, 21, 18, 26, 47, 22, 13, 16, and 14, respectively. b, Effects of the GABAB antagonist CGP 35348 and the GABAAantagonist picrotoxin on network oscillation frequency are shown. In control conditions, the oscillation frequency is 6–7 Hz in spontaneous spindle waves (no stimuli) and with one stimulus per cycle, whereas it is ∼3 Hz when bursts of six stimuli are used. In the presence of CGP 35348, the oscillation frequency remains at 6–7 Hz whether one or six stimuli are given. In picrotoxin, the oscillation frequency is ∼3 Hz regardless of whether one or six stimuli are given. Group frequency data are shown from 13 intracellular and 3 extracellular recordings in which one or both drugs were applied. Mean and SEM values for all frequencies are listed in Results. The following frequency changes were significant at the p < 0.0001 level (two-tailedt test): control one stimulus versus control six stimuli, control six stimuli versus CGP 35348 six stimuli, and control one stimulus versus picrotoxin one stimulus.