Figure 4.
BGMT neurons from 6-OHDA-treated mice showed stronger rebound burst firing. A–C, Single BGMT neuron voltage traces from representative control (left) and 6-OHDA (right) mice showing responses to 50-, 100-, 150-pA hyperpolarizing stimulus steps at durations of 0.2, 0.5, or 2 s. Dashed rectangles mark rebound bursts expanded in the inset windows to the left. D–F, Bar graph pairs represent the average number of action potentials per rebound burst ± SEM in controls (black bars) and in 6-OHDA-treated mice (white bars). Data were sorted by the amplitude of hyperpolarization reached at the end of the step current hyperpolarizing current pulse (step amplitudes ranged from −50 to −500 pA at 50-pA increments). Using this measure instead of the current injection amplitude avoids conflating rebound properties because of voltage-dependent channel de-inactivation with different levels of hyperpolarization reached because of passive Rin of differently sized neurons. Before step current injection, a tonic bias current (CON: 90.7 ± 15.7 pA; 6-OHDA: 54.1 ± 16.07 pA) was adjusted to maintain the membrane potential at a similar level for all neurons (average of −56.52 ± 0.6 mV), again to test for rebound properties under comparable voltage levels. The results show that the number of APs was increased up to 80% in neurons from 6-OHDA-treated mice, which was significant for almost all stimulus conditions (see Table 2).
Figure Contributions: Edyta K. Bichler conducted experiments, performed statistical analysis, and prepared figure. Dieter Jaeger reviewed data and analysis.