Figure 4.

Contribution of I_h to subthreshold resonance in GCs. A, Top, Voltage responses (top traces) to a ZAP current stimulus (bottom traces) in MOB GCs in a resonant (left) and, a nonresonant (right) cell. Bottom, Impedance profiles for the cells shown above. In the resonant cell (left), the Q value is 1.20 and the f_res value is 3.88 Hz; whereas, for the nonresonant cell (right), f_res = f_low and the Q = 1. Calibration: 5 s and 10 mV [with a 50 pA (left) and 5 pA (right) ZAP stimulus amplitude]. The V_m for both cells is −80 mV. B, ZAP stimulus applied to resonant GCs in the MOB (top) and AOB (bottom); the current amplitude was adjusted to elicit action potentials, which occurred around the resonant frequency of the cell. C, Top, The impedance profile of an AOB GC that exhibits subthreshold resonance in control conditions and, in the presence of ZD7288. In control conditions, Q = 1.21 and f_res = 1.3 Hz (black line). In the presence of ZD7288, the resistance of the GC increases, the resonance is abolished, and the impedance profile resembles that of a nonresonant cell (Q = 1). Bottom left, Summary plot showing the distribution of values for maximal I_h (measured at −130 mV) for MOB (blue, n = 19) and AOB (orange, n = 21) GCs; resonant cells have larger I_h values. Bottom right, The Q factor significantly decreases after perfusion of ZD7288 in the AOB (n = 4) and MOB (n = 4).