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Fig. 4. The muscarinic acetylcholine agonist oxotremorine routinely activated the
pyloric pattern in preparations in which the stn was blocked with
isotonic sucrose, and there thus was no ongoing pyloric pattern. (A)
Representative recordings of pyloric activity in a preparation with conduction
in the stn blocked with isotonic sucrose and superfused with normal
saline, then superfused with oxotremorine (10–7 mol
l–1), followed by a wash in normal saline. A complete core
pyloric pattern, with intense firing in all three neuronal types (PD, LP, and
PY) was induced by the oxotremorine (seen in pdn, PD, and
lvn, PD, LP and PY, recordings); in contrast, regular bursting was
not initiated in the VD and IC neurons (mvn). (B) Phase plot, showing
two cycles of the pyloric pattern recorded in oxotremorine, taken from four
preparations, showing that oxotremorine activated the core pyloric pattern,
but not the VD and IC neurons. (C) Graph of average cycle period: in control
saline there was no activity, while cycle period was approximately 4 s in the
presence of oxotremorine (Oxo); this is somewhat longer than cycle period in
control saline when the stn is not blocked (approximately 3.3 s in
Fig. 3, for example.) (D,E)
Graphs of the spike frequency during bursts and burst duration in each
neuronal type during oxotremorine superfusion with the stn blocked.
Because there was no rhythmic activity, and therefore no bursts in any of the
neurons, values during saline superfusion are not shown. N=4 for all
graphs. Bars indicate standard deviations. Nerves: mvn, medial
ventricular nerve (recording action potentials of the VD and IC neurons);
pdn, pyloric dilator nerve (recording action potentials of the PD
neurons); lvn, lateral ventricular nerve (recording action potentials
of the PD, LP and PY neurons).
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