Effects of intestinal inflammation on specific subgroups of guinea-pig celiac ganglion neurons.

The consequences of inflammation of a short region of the guinea-pig ileum on the properties of neurons in the celiac ganglia were investigated. Inflammation (ileitis) was induced in 5–8cm of intestine by the intralumenal injection of trinitrobenzene sulfonate, 6–7 days before tissue was taken. Celiac ganglion neurons were investigated using intracellular microelectrodes and the cells were filled with dye from the recording electrode, to determine their morphologies. Tonic and phasic neurons were identified. In ganglia from normal guinea-pigs and from guinea-pigs with ileitis, cell bodies of tonic neurons were larger and their dendrites were longer and more numerous than those of phasic neurons. Tonic neurons were selectively affected by intestinal inflammation. The number of action potentials elicited by the same intensity of depolarizing current for neurons after ileal inflammation was twice that of neurons from control animals, the threshold current to evoke action potentials was about half, and some of the neurons were spontaneously active. Neurons from untreated or sham-operated animals were never spontaneously active. Many more neurons were affected than project to the 5–8cm of intestine that was inflamed. We conclude that inflammation of a segment of the ileum causes a selective, humorally mediated, increase in excitability of tonic neurons in the celiac ganglion that control motility and secretion, but not of phasic neurons that project to the intestinal vasculature and other targets.