Figure 4.

SP excites Cd²⁺-insensitive pacemaker activity. A, Example of a Cd²⁺-insensitive pacemaker neuron that continues to burst rhythmically (bottom trace) in the absence of rhythmic population activity (top trace). The SP-induced slow depolarization increases bursting in this type of pacemaker. B, Same pacemaker neuron as A in an expanded time scale showing burst activity before (left) and during SP-induced slow depolarization (right). C-E, Histograms characterizing bursting properties of Cd²⁺-insensitive pacemaker neurons before [control (CON)] and during SP application. The asterisk denotes statistically significant differences (p < 0.05).