Figure 3. Transient local stimulation with AMPA pulses evokes XII motor output (XII_evoked) following short (∼1 s) and long (60 s) intervals following endogenous XII output.

The interval of stimulation following endogenous XII output is defined as Δt_stim. A, lowering [K⁺]_o from 9 to 3 mm slowed the respiratory rhythm to 0.008 Hz. The top trace (V_M) shows a whole-cell recording from a neuron in the preBötC. Baseline voltage was −60 mV at the start of the sweep. The lower trace shows XII output. Lower insets show XII_evoked cycles at higher sweep speed following long (a) and short (b) stimulation. The 2 s calibration bar applies to both inset traces. a, after two successive cycles with a period of ∼120 s, local AMPA stimulation was applied 60 s after the endogenous XII output (i.e. Δt_stim= 60 s), which evoked three rapid cycles of XII_evoked with a latency (Δt_evoked) of 1 s. b, after the first stimulation protocol (a), the cycle period returned to ∼120 s, and after two consecutive cycles, another local AMPA stimulation was applied 1.1 s following the endogenous XII output (i.e. Δt_stim= 1.1 s), which evoked four rapid cycles of XII_evoked with a latency (Δt_evoked) of 3.5 s. B, the normalized amplitude (open circles), half-width (open squares), and area (open triangles), of XII_evoked from the experiment in A are plotted versus Δt_stim. C, Δt_evoked of the bursts from the experiment shown in A are plotted versus Δt_stim. The dotted line in B is a horizontal reference for normalized XII output = 1; dotted line in C is a linear regression fit to the data.