AJP - Gastrointestinal and Liver Physiology, Vol 243, Issue 4 259-G267, Copyright © 1982 by American Physiological Society
Effect of substance P on colonic mechanoreceptors, motility, and sympathetic neurons
J. Krier and J. H. Szurszewski
Intracellular recording techniques were used in vitro to analyze the
effects of substance P (SP) on synaptic transmission and electrical
properties of sympathetic neurons in the inferior mesenteric ganglion (IMG)
of the guinea pig. Intraluminal pressure-recording techniques were used to
study the effects of SP on colonic motility. Superfusion of the ganglia
with SP (10(-7) to 10(-6) M) depolarized the cell soma (2--12 mV) and
increased cell input resistance (8--11 M omega). These effects converted
synchronous excitatory postsynaptic potentials, in response to electrical
stimulation of preganglionic nerves, and asynchronous excitatory
postsynaptic potentials, in response to activation of colonic
mechanoreceptors, to action potentials. Administration of SP to only the
colon increased basal intraluminal pressure and the frequency and amplitude
of phasic changes in intraluminal pressure. These changes increased
mechanoreceptor synaptic input to neurons in the IMG. We conclude that SP
facilitates synaptic transmission along noradrenergic pathways and
increases colonic motility.
