Distribution pattern and chemical coding of neurons of the sympathetic chain ganglia supplying the descending colon in the pig

Sympathetic chain ganglia (SChG) neurons projecting to the descending colon of the pig were studied by means of retrograde tracing (Fast Blue, FB) and double-labelling immunofluorescence methods. FB was injected into the gut wall and after three weeks survival time the animals were transcardially perfused with paraformaldehyde and the bilateral sympathetic trunks were collected. The FBpositive neurons were localised only in the lumbar (L1–L5) ganglia of the sympathetic trunk and appeared either as small (30–50 μm in diameter) round-shaped perikarya forming clusters localised in caudal-ventral area or, rarely, as bigger (50–80 μm) and dispersed solitary irregular perikarya. Immunohistochemical staining revealed the catecholaminergic (tyrosine hydroxylase-/dopamine β-hydroxylase-immunoreactive) character of the great majority of FB-positive neurons which preferentially co-expressed neuropeptide Y. In addition, none of the FB-positive perikarya was immunopositive to galanin, somatostatin, choline acetyltransferase, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, leu5-enkephalin, nitric oxide synthase, substance P and calcitonin-generelated peptide