FIG. 2.
Membrane properties of the multicompartment cable models of GPi neurons were fit to data from in vitro studies of rat entopeduncular nucleus (EP) neurons (Nakanishi et al. 1990; Shin et al. 2007). A: simulations of somatic activity yielded comparable action potential and resting membrane potential characteristics to those observed experimentally. B: the firing rate depended on the conductance of the sodium leakage channels (gNaL), and this parameter was used to tune the model to produce firing rates consistent with in vitro EP neurons (18 μS/cm2) as well as in vivo GPi spike recording data (28 μS/cm2) from nonhuman primates. C: current–frequency plots demonstrated that model neurons could generate high firing rates during intracellular current injection with (D) little spike accommodation. E: in a hyperpolarized state, model neurons also responded to a depolarizing pulse with both short-duration sodium and long-duration calcium spikes (compare with Fig. 2 from Nakanishi et al. 1990). F: using a gNaL of 18 μS/cm2, simulations were able to capture hyperpolarization-activated currents that (G) were consistent with experimental recordings (compare with Fig. 1 from Nakanishi et al. 1990).