Fig. 5.

AMPARs expressed in different types of basal ganglia neurons differ in Ca²⁺ permeability. A, B, I–V relations of glutamate-activated peak currents recorded from nucleated patches in Na⁺-rich (open circles) and Ca²⁺-rich (30 mm,filled circles) external solution. A, Patch from a dopaminergic neuron of the substantia nigra pars compacta.B, Patch from a subthalamic nucleus neuron. Recordings of glutamate-activated currents at −100 mV and +50 mV are shown asinset: top traces in Na⁺-rich solution and bottom traces in Ca²⁺-rich external solution. The continuous curves represent polynomials of the fifth order fit to the data points. Reversal potentials in Ca²⁺-rich solution are indicated byarrows. C, Bar graph of the average relative Ca²⁺ permeability (P_Ca/P_Na) of AMPARs expressed in the types of basal ganglia neurons investigated, determined from the reversal potentials of glutamate-activated currents in Na⁺-rich and Ca²⁺-rich external solution. All data are from nucleated patches. External solutions contained 50 μmd-AP5 in all cases.