Figure 4.

Suppressing the pyloric rhythm did not eliminate the POC- or VCN-gastric mill rhythm but did change the fast rhythmic LG burst pattern to a tonic pattern during the POC rhythm. A, The POC-gastric mill rhythm persisted when the pyloric rhythm was suppressed by hyperpolarizing the pyloric pacemaker (AB/PD) neurons, but it slowed and the pyloric-timed LG burst pattern (left) was changed to a tonic pattern (right). B, The VCN-gastric mill rhythm persisted, albeit with a longer cycle period, when the pyloric rhythm was suppressed. Note that the LG burst pattern remained tonic in the absence of the pyloric rhythm. C, Comparison of the LG instantaneous spike frequency distribution during the POC-gastric mill rhythm in the presence versus absence of the pyloric rhythm. Note that suppressing the pyloric rhythm resulted in an ∼12-fold decrease in the number of events between 1.5 and 3 Hz (PR on, 235 events; PR off, 19 events). This range included most (91%: 235 of 259) of the pyloric rhythm (PD neuron)-timed interruptions in the LG burst. The first bar (0–0.5 Hz) for each condition represents the retractor phase. Bin width is 0.5 Hz. Total number of events: PR on, 2550; PR off, 4702. Data are from five preparations (10 gastric mill cycles per preparation for each condition).