Figure 5.

Viscerofugal neuron burst firing characteristics. A, The duration of 1676 individual bursts of firing in rectal nerves during 31 motor complexes in six organ cultured preparations shown as a frequency distribution. B, Distribution of the average numbers of action potentials each unit contributed to each burst in rectal nerves. Single units did not contribute to every instance of burst firing in rectal nerves, as may be seen in Figure 4. This highlights the importance of synchronization among multiple neurons, since single units alone were unlikely to encode the entire burst firing pattern. Single units contributed between 0 and 12 action potentials to a burst of firing. C, D, Comparisons of CMC smooth muscle firing rate and duration in control and cultured preparations, showing no significant differences between the two groups (p = 0.200 and 0.069, respectively, independent samples t test). Estimated mean differences between the groups are shown in a separate graph to the right. E, F, Average single unit firing rates before, during and after CMCs among units that contributed to burst firing behavior (E) and those that did not (F). All data are paired, and mean differences are shown graphically below mean firing rates. Firing in single units increased by 1–3 Hz among those that contributed to burst firing during the CMC compared with before or after CMCs, but not among those that did not contribute to burst firing (F). See text for details. G, The effect of hexamethonium on ongoing firing rate was significant among contributing but not non-contributing burst firing units.