CRF increases depolarization-induced spiking. Whole-cell current-clamp recordings of action potentials generated by intracellular (through the patch electrode) injections of depolarizing current pulses (500 ms) of increasing magnitude (in 50 pA steps) from a membrane potential of −60 mV. (A, B) Upper traces show action potential firing rate increased during superfusion of CRF (10 nM, 12 min). Lower traces show depolarizing current steps. Graphs show input–output functions (frequency-current [F-I] relationships) averaged for each sample of neurons. CRF increased F-I relationships significantly (A, n = 5 neurons; P < 0.0001, F1,56 = 14.87; B, n = 5 neurons; P < 0.0001, F1,56 = 15.68; compared to predrug, two-way ANOVA). (A) A CRF1 receptor antagonist (NBI27914, NBI, 1 μM, n = 5) blocked the effect of CRF significantly (P < 0.0001, F1,56 = 14.53, two-way ANOVA). (B) A CRF2 receptor antagonist (astressin-2B, AStr2B, 1 μM, n = 5) had no significant effect (P > 0.05, F1,56 = 0.89, compared to CRF, two-way ANOVA). Symbols and error bars represent means ± SEM.