Figure 1. Cadmium-sensitive calcium channels make a significant contribution to the spontaneous activity of the majority of DCN neurons.

Spontaneous activity of individual, visually identified DCN neurons was monitored by extracellular recording in acutely prepared slices at 35°C. Fast excitatory and inhibitory synaptic transmission was blocked pharmacologically. Aa, application of cadmium increased the firing rate and caused random bursts of action potentials in the majority of DCN neurons. Sample raw data traces are shown in the right panel. Ab, interspike interval histogram of the cell shown in Aa. Ac, predominant and maximum spontaneous firing rates of individual cells together with the averages in the presence and absence of cadmium. *P < 0.001, n = 33 cells. Ad, the coefficient of variation of the interspike intervals for the same cells shown in Ac. *P < 0.001. Ba, in a small fraction of cells cadmium simply reduced the firing rate. Sample traces are shown to the right of the panel. Bb, interspike interval histogram of the cell shown in Ba. Bc, predominant and maximum spontaneous firing rates of individual cells together with the averages in the presence and absence of cadmium. *P < 0.01, n = 11 cells. Bd, the coefficient of variation of the interspike intervals for the same cells shown in Bc. *P < 0.001. Be, the predominant firing rate of all cells examined (in A and B) before and after addition of cadmium. The continuous line represents the unity line.