Inactivation mode of sodium channels defines the different maximal firing rates of conventional versus atypical midbrain dopamine neurons
Fig 3
Known differences between atypical and conventional populations do not fully account for differences in peak firing rate or failure mode.
A. Effects of varying maximal HCN conductance on A1, the minimum depolarizing current ramp amplitude required to induce depolarization block and A2, the peak firing rate (red) and number of evoked spikes (blue) on entry into depolarization block at the ramp amplitude from the previous panel. Dashed lines indicate values used for control and representative value in F-I. A1. B. Same as A except varying the Kv4 inactivation time constant. C. Same as A except varying the maximal SK conductance. D Same as A except varying the delayed rectifier and the sodium current by the same scale factor. E. Atypical control as in Fig 2B2 except in response to 75 pA ramp. Dashed line indicates time of first spike for control. Scale bar: 20 mV and 1 s. F. Increased H conductance. G. Faster Kv4.3 inactivation time constant. H. Elevated SK conductance in response to 110 pA ramp. I. Effect of increasing the primary spiking conductances (voltage gated sodium and the delayed rectifier) by an identical factor of 2 in response to 250 pA ramp. F. All parameters are set to atypical values in Table 1 except the parameter that is varied. The spike scale factor proportionally scales both gK,dr and gNa,V.