Table 1.

Electrophysiological parameters of DA and Gaba neurons in the SN and VTA

	Spike threshold	fAHP	Spike width	Ih Sag	Firing frequency
DA (n = 55) 24/9/22	−34  ± 1 mV	20  ± 1 mV	2.62  ± 0.08 msec	39  ± 3%	2.4  ± 0.3 Hz (n = 24)
Gaba (n = 24) 3/11/10	−42  ± 1 mV	13  ± 1 mV	1.32  ± 0.09 msec	9  ± 2%	17.2  ± 3.1 Hz (n = 11)

Number of neurons in each of the SNc/SNr/VTA is indicated below neuron class label. All quantified parameters were significantly different (p < 0.001) between DA and Gaba neurons. Fast afterhyperpolarization (fAHP) was measured from threshold; spike width was measured at threshold; I_h sag quantifies the time-dependent relaxation in the voltage response to hyperpolarizing current steps, indicative of I_hcurrent activation; firing frequency was evaluated at the resting membrane potential in spontaneously active neurons.