Figure 1.
SP excites the respiratory network and depolarizes respiratory neurons. A, Schematic showing anatomical landmarks of a slice from the neonatal mouse medulla and recording sites for both population activity [integrated VRG (∫VRG)] and whole-cell patch-clamp recordings [membrane potential recording (VM)]. Note that application of 0.75 μm SP induces an excitation of integrated population activity (top trace) that is accompanied by a slow depolarization of a rhythmic neuron (bottom trace). The constant hyperpolarizing pulse was applied to test any change in input resistance produced by the application of SP. IO, Inferior olive; NA, nucleus ambiguus; SP5, spinally projecting trigeminal nucleus; XII, hypoglossal nucleus. B, Time course of the effect of SP on integrated population burst frequency. After 3 min of control recording, 0.75 μm SP was added (arrow) and continued for the rest of the experiment (n = 13). C, Time course of the effect of SP on the irregularity score (see Material and Methods) of respiratory activity. Note that after application of SP (arrow), the irregularity score is considerably reduced, indicating that the rhythm became more regular (n = 13). D, Quantification of resting membrane potential before [control (CON)] and after SP application for 15 respiratory neurons showing a significant depolarization. The asterisk denotes a statistically significant difference (p < 0.05). E, Comparison of a constant hyperpolarizing pulse as in A before (Control) and during application of SP, showing that there is no change on input resistance accompanying the depolarization induced by SP.