AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 6 437-G441, Copyright © 1981 by American Physiological Society
Synaptic activation of erratic burst-type myenteric neurons in cat small intestine
G. R. Athey, A. R. Cooke and J. D. Wood
To study further the ongoing spike discharge of burst-type myenteric
neurons, extracellular recordings were made with either Teflon-insulated Pt
wire electrodes (tip diam, 20 micrometers) or 3 M NaCl-filled glass
micropipettes (tip diam, 1-2 micrometers). Presynaptic fibers to the
erratic bursters were activated by electrical shocks delivered through
Teflon-insulated Pt wire electrodes. Single electrical shocks applied to
either the surface of the ganglion or an interganglionic connective
elicited bursts of spikes that had parameters (interspike intervals and
spikes per burst) that closely resembled the spontaneously occurring bursts
in the same neuron. The latencies of the responses to electrical
stimulation ranged from 5 to 30 ms. The responses were reversibly abolished
when the concentration of Mg2+ in the bathing solution was elevated to 12
mM. The responses to electrical stimulation were unaffected by atropine,
hexamethonium, d-tubocurarine, epinephrine, norepinephrine, methysergide,
morphine, naloxone, and substance P. The ongoing burst-type discharge of
cat myenteric neurons appeared to reflect a synaptic event that could be
mimicked by electrical stimulation of presynaptic fibers. The identity of
the neurotransmitter that elicits the burst-type discharge is unknown. The
transmitter is probably not acetylcholine, serotonin, norepinephrine, an
opiatelike peptide, nor substance P.
