Figure 8.

Cd²⁺ blockade of voltage-gated Ca²⁺ channels inhibited manganese stimulation of spontaneous firing activity of dopamine neurons. A, Top, Representative spontaneous spike activity of a dopamine neuron before and after exposure to Cd²⁺ (a nonselective voltage-gated Ca²⁺ channel blocker) and Cd²⁺ + Mn²⁺. Cd²⁺ blockade of voltage-gated Ca²⁺ channels inhibited Mn²⁺ stimulation of spontaneous firing activity. Bottom, Histogram of firing frequency from above trace showing that firing frequencies were lowered in Cd²⁺ only condition and following or Cd²⁺ + Mn²⁺ but return to baseline after washout. B, Superimposed representative single AP traces shown in A: baseline (black trace), 100 μm Cd²⁺ (green trace), 100 μm Mn²⁺ + Cd²⁺ (red trace), and washout (blue trace). C, Spontaneous firing rate significantly decreased following application of Cd²⁺ or Cd²⁺ + Mn²⁺ (F_(2,18) = 8.3, p = 0.002, one-way ANOVA followed by Tukey's test, n = 7/group). D, Application of Cd²⁺ or Cd²⁺ + Mn²⁺ did not change the membrane potential. E, Half-width was measured at half-maximal voltage of AP; there was no change in the half-width of the Cd²⁺ and Cd²⁺ + Mn²⁺ experimental groups. F, Cd²⁺ or Cd²⁺ + Mn²⁺ treatments did not change the amplitude of AP. G, Both Cd²⁺ and Cd²⁺ + Mn²⁺ treatments increased the CVs of the interspike interval (F_(2,18) = 4.6, p = 0.024, one-way ANOVA followed by Tukey's test, n = 7/group). *p < 0.05, **p < 0.01.