Figure 3.

SP potentiates Cd²⁺-sensitive pacemaker activity. A, Example of a Cd²⁺-sensitive pacemaker neuron that continues to burst rhythmically (bottom trace) in the absence of rhythmic population activity (top trace). The recording was obtained in the presence of the mixture. The SP-induced slow depolarization is accompanied by a dramatic increase in burst generation leading to action potential inactivation. Note also the amplitude of bursting was affected during the peak depolarization, suggesting also the inactivation of the burst mechanisms themselves. Injection of the constant negative DC current (arrow) restores burst and action potential generation. The neuron presented was previously confirmed as an inspiratory neuron in the absence of the mixture. B, Same pacemaker neuron as A in an expanded timescale showing burst activity before (left), at the beginning of the SP-induced slow depolarization before action potential inactivation (middle), and after applying negative DC current to restore action potential activity (right). C-E, Histograms characterizing bursting properties of Cd²⁺-sensitive pacemaker neurons before [control (CON)] and during SP application. The asterisk denotes a statistically significant difference (p < 0.05).