Fig 6.

Theophylline hyperpolarizes neurons by potentiating calcium-activated potassium currents. A,Left panel, Box-and-whisker graph showing the range of membrane potentials at rest. Middle panel, Trace of membrane potential change recorded during incubation with vehicle or theophylline in current clamp mode (I = 0) and perforated patch whole-cell configuration. Right panel, histogram of the averaged resting membrane potential change recorded on 4 cells. Data are expressed as means ± SEs. *P < .05 compared with the control (vehicle, 0.1% dimethyl sulfoxide) using the Mann-Whitney U test. B, Currents were elicited by 800-ms square depolarizing pulses from −100 mV up to +120 mV with a 10-mV increment and −70 mV holding potential. The zero current levels are indicated by an arrow on the left of the traces. Left panel, Clotrimazole (10 μmol/L)–sensitive current obtained under control (0.1% dimethyl sulfoxide) conditions and after incubation with theophylline. Right panel, Current density-voltage relationships in the control condition (open circles, n = 4) and after incubation with theophylline (0.1 μmol/L, solid circles, n = 4). *P < .05. C, Left panel, Apamin (1 μmol/L) sensitive current obtained control condition (0.1% dimethyl sulfoxide) and after incubation with theophylline. Right panel, Current density-voltage relationships under control conditions (open circles, n = 4) and after incubation with theophylline (0.1 μmol/L, solid circles, n = 4). Data are expressed as means ± SEs. Current density amplitudes were compared by using 2-way ANOVA and Bonferroni post hoc tests. *P < .05.