Fig. 1.
Electrophysiological characteristics of substantia nigra pars reticulata (SNr) GABA neurons and nigral dopamine projection (DA) neurons. A: electrophysiological properties of SNr GABA neurons. Current-clamp recordings show spontaneous high-frequency activity and minimal hyperpolarization-activated current (Ih)-mediated depolarizing sag in response to hyperpolarizing current injection. B: electrophysiological properties of nigral DA neurons. Current-clamp recordings show spontaneous low-frequency pacemaker activity and prominent Ih-mediated depolarizing sag (arrow) in response to hyperpolarizing current injection. C: overlay of a GABA neuron spike and a DA neuron spike, showing the clear differences in the spike waveform between the two cell types. D: SNr GABA neurons show little firing frequency and amplitude adaptation to depolarizing current injection (150 pA). E: nigral DA neurons show prominent firing frequency and spike amplitude adaptation to depolarizing current injection (100 pA). Recordings were made with a 135 mM KCl-based intracellular solution.