Intrinsically oscillatory bursting neurons in the preBötC. (A) Schematic representation of the neonatal rat medullary transverse slice preparation (thickness: 300–350 µm), containing the inspiratory rhythm-generating circuits in the preBötC, with output to the hypoglossal motor nucleus. 5SP, spinal trigeminal nucleus; IO, inferior olivary nucleus; NA, nucleus ambiguus; V4, fourth ventricle; XII, hypoglossal motor nucleus. (B) With synaptic transmission intact, inspiratory neurons exhibit rhythmic bursting activity (upper trace, CC recording) in synchrony with inspiratory network activity (lower trace, XII motor nerve inspiratory discharge). (C) Intrinsic bursters maintain voltage-dependent rhythmic bursting activity (upper traces) when network-wide synaptic transmission is disrupted by bath-applied CNQX, which blocks non-NMDA glutamatergic receptors. No rhythmic XII nerve output can be observed (lower traces). Neuronal bursting frequency is a function of baseline membrane potential and can be modulated by injecting current (I_app, middle traces). (D) Intrinsic bursting activity is not significantly affected by bath-applied Cd²⁺, which inhibits calcium-related currents. The inset illustrates the characteristic bAHP and the slow depolarization drift (arrow). (E) Representative burst (gray trace) and statistical measures. The data points (mean and SD) were calculated at 0%, 25%, 50%, 75%, and 100% of burst time and were obtained from 19 neurons by averaging over five consecutive bursts in each neuron. All CC traces were obtained from representative neurons. AP, action potential.