Identification of intestinofugal neurons projecting to the coeliac and superior mesenteric ganglia in the rat

Intestinofugal neurons are parts of the afferent limbs of inhibitory intest ino-intestinal reflexes. These neurons have been mapped in guinea-pigs, whe re they have a gradient of increasing frequency of occurrence from oral to anal, but not in other species. In the present work in the rat, a species t hat is more amenable to physiological study than the guinea-pig, we have us ed retrograde tracing to map the distribution of the cell bodies of intesti nofugal neurons projecting to the coeliac-superior mesenteric ganglion comp lex. Labelled nerve cells were found in the myenteric, but not the submucos al plexus. They were mono-axonal neurons, most with Dogiel type I morpholog y, and were immunoreactive for choline acetyltransferase, implying that the y are cholinergic, which is consistent with functional studies. The cells i ncreased in number per unit area from the stomach, through the small intest ine, to the caecum. The results are consistent with physiological studies t hat reveal distal to proximal inhibitory reflexes that are more potent from distal compared to proximal sires. (C) 2000 Elsevier Science B.V. All righ ts reserved.