Extrinsic afferents supplying the ovine duodenum and ileum

The study aimed at establishing the distribution of primary sensory neurons by means of retrograde tracers Diamidino Yellow (DY) and Fast Blue (FB) injected into both the sheep duodenum and ileum, respectively. Many DY-labelled cells were found in both the distal vagal ganglia (DVG) and the spinal ganglia (SG) from T9–L3; on the contrary, the majority of the FB-labelled cells were found in the SG. In the SG, a double immunofluorescence stain was used to reveal Nitric Oxide Synthase-Immunoreactivity (NOS-IR) in association with: substance P (SP), calcitonin gene-related peptide (CGRP), neurofilament 200 kDa (NF) and isolectin B4 (IB4). The labelled neurons, both DY and FB generally ranged in size from medium to large. The majority of the SG duodenal projections were NOS negative; the majority of the SG ileal afferent neurons expressed NOS-IR. Both DY and FB NOS-IR neurons often co-localized IB4, CGRP and SP, but rarely NF.