Fig. 4.

Pentobarbital sodium produces similar effects in lower bath [KCl]. A: responses are shown for VRC, NTS, and cortical neurons in slices from IBA squirrels exposed to 5 mM KCl and 150 μM pentobarbital sodium (open bars) compared with 9 mM KCl and 300 μM pentobarbital sodium (solid bars). The data show the mean normalized firing rate during the last 5 min of a 60-min drug application. B: dose-dependent effects of sodium pentobarbital on spontaneous activity of VRC, NTS, and cortical neurons in slices from IBA squirrels are shown. The pentobarbital sodium concentrations that were tested include 300 μM (solid bars), 200 μM (dark gray bars), and 100 μM (light gray bars). IBA time controls (open bars) are shown. Spontaneous activity was unaltered at all three concentrations in VRC neurons (300 μM, n = 54; 200 μM, n = 48; 100 μM, n = 53; time control, n = 40) and NTS neurons (300 μM, n = 29; 200 μM, n = 14; 100 μM, n = 13; time control, n = 12). In contrast, spontaneous activity in cortical neurons was unaltered at 100 μM (n = 46), decreased by 78 ± 6% at 200 μM (n = 43; †P < 0.001) and decreased by 89 ± 1% at 300 μM (n = 79; †P < 0.001) compared with time controls (n = 22). The mean normalized firing rate represents the average during the last 5 min of a 60-min drug application. Error bars indicate means ± SE.