Effect of decentralization on parameters of I_A in PD neurons after 6 d in organ culture. All values are means ± SEM (control preparation,n = 7; decentralized preparations,n = 8). A, Time-to-the peak current as a function of membrane potential for activation ofI_A in PD neurons under control conditions (open circles) and in decentralized preparations (filled circles). The time-to-peak current did not differ significantly between the two conditions. B,C, During a maintained voltage pulse,I_A decays with two time constants, τ₁ (fast) and τ₂ (slow). Both time constants did not differ significantly between control conditions and decentralized preparations, as demonstrated for τ₁(B) and τ₂(C) for a voltage pulse to +50 mV.D, Conductance–voltage curves for activation (circles) and inactivation (squares) ofI_A under control conditions (open symbols) and in decentralized preparations (filled symbols). Values are calculated as a fraction of the maximal conductance under control conditions in each experiment. The activation curves were generated from peak currents after a maximally de-inactivating prestep to −120 mV. The curves are fits to a third-order Boltzmann relation (Eq. 1, Materials and Methods) with the following parameters: control,V_act = −41.7 mV, s= −17.7 mV; decentralized, V_act = −38.2 mV, s = −18.9 mV. The curves for steady-state inactivation were generated from peak currents to voltage pulses to +50 mV after the neurons were held at the indicated potential (prepulse) for 1.5 sec. The curves are fits to a first-order Boltzmann relation (Eq. 1, Materials and Methods), with the following parameters: control, V_inact = −63.2 mV,s = 6.0 mV; decentralized,V_inact = −61.3 mV,s = 6.5 mV. E, Maximal current amplitude elicited by voltage pulses to +70 mV. After decentralization, the mean maximal current amplitude was significantly increased by 43.4%, from 313.6 ± 24.3 nA to 449.6 ± 27.7 nA (*p < 0.01).