The projections of chemically identified nerve fibres in canine ileum

Abstract

The projections of nerve fibres with immunoreactivity for the peptides enkephalin (ENK), gastrin-releasing peptide (GRP), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP) and vasoactive intestinal peptide (VIP) were studied in canine small intestine by analysing the consequences of lesions of intrinsic and extrinsic nerves. Of peptides present in fibres supplying myenteric ganglia, GRP, SOM and VIP were in anally directed nerve pathways, whereas ENK and NPY were in orally directed pathways. Pathways ran for up to about 30 mm. SP fibres ran for short distances in both directions in the myenteric plexus. The circular muscle was supplied with ENK, NPY, SP and VIP fibres arising from the myenteric ganglia, whereas most mucosal SP and VIP fibres were deduced to arise from submucous ganglia. There were projections of fibres reactive for ENK, GRP, SOM, SP and VIP from myenteric ganglia to submucous ganglia. Antibodies to tyrosine hydroxylase were used to locate noradrenaline nerve fibres supplying the intestine; these fibres all disappeared when extrinsic nerves running through the mesentery to the small intestine were cut. It is deduced that there is an ordered pattern of projections of peptide-containing fibres in the canine intestine.

Projections of enteric peptide-containing neurons in the rat.

“…In the guinea pig, both VIP and NPY neurons issue descending projections (c. f. FUR-NESS and COSTA, 1987), in the dog VIP neurons issue descending projections while NPY neurons issue ascending ones (DANIEL et al, 1987). It is also apparent that the structural organization and chemical coding of enteric neurons is not identical in all segments of the gut, as illustrated by our findings in the rat (see EKBLAD et al, 1987EKBLAD et al, , 1988.…”

“…Rat Guinea-pig Dog guinea pig (c. f. FURNESS and COSTA, 1987) and dog (DANIEL et al, 1987), VIP and NPY seem to be stored in separate neurons. In the guinea pig, both VIP and NPY neurons issue descending projections (c. f. FUR-NESS and COSTA, 1987), in the dog VIP neurons issue descending projections while NPY neurons issue ascending ones (DANIEL et al, 1987).…”

“…This is reflected in the finding that each population of enteric neurons displays a characteristic distribution and an equally characteristic projection pattern, as revealed by the lesion experiments. So far this type of study has been performed in a limited number of species, namely the guinea pig (c. f. FURNESS and COSTA, 1987), rat (EKB-LAD et al, 1987, 1988, and dog (DANIEL et al, 1987). The projections of the peptide-containing myenteric neurons in the small intestine of the three species are compared in Figure 10, from which it is evident that the projection patterns are fairly similar in these species.…”

“…In the rat, NPY and VIP coexist in neurons which issue descending projections (EKBLAD et al, 1987). In the , 1980, 1981COSTA and FURNESS, 1983;DANIEL et al, 1987;FURNESS and COSTA, 1987;EKBLAD et al, 1987. There are many similarities in the projection pattern among the three species.…”

Correlated functional and structural analysis of enteric neural circuits.

“…More-over, motor and sensory neurons are distinguishable electrophysiologically and some of their chemical characteristics have been established. The cell bodies of the motor neurons that supply the circular muscle coat are deduced to be in the myenteric plexus, because it has been shown that all nerve fibres of intrinsic origin that supply this layer come from the myenteric plexus in the guinea-pig small intestine (WILSON et al, 1987), and probably also in the dog small intestine (DANIEL et al, 1987). The longitudinal muscle of the guinea-pig small intestine is functionally innervated but it is not obvious from structural studies which fibres provide this innervation.…”