Fig. 2.
DA induced positive shifts in the voltage dependence of LP IA. A: TEVC recordings under control conditions, with 10 min bath application of 10−5 M DA and after 30 min washout of DA. Current traces were obtained in response to a series of depolarizing test pulses (from −50 to +60 mV in 10 mV increments) following a hyperpolarizing prepulse to −90 mV. All voltage dependent ion channels except IA were pharmacologically blocked. Scale bars represent 100 ms and 50 nA. B: normalized conductance–voltage plots for activation (○, □, ▵) and inactivation (●, ■, ▴) fit with a 1st-order Boltzmann equation. Plots were obtained under control condition (□, ■), with 10 min 10−5 M DA application (○, ●), and after 30 min washout of DA (▵, ▴) n ≥ 5 for each data point. C and D: preparation-to-preparation variability. ○, the IA V1/2 activation (C) and inactivation (D) for a single individual in the presence (y axis) versus absence (x axis) of 10−5 M DA. The line indicates unity and points above and below the line indicate that DA shifted the V1/2 to more depolarized or hyperpolarized potentials, respectively.