IMMUNOCYTOCHEMICAL LOCALIZATION OF THE NEURONS IN THE SUPERIOR MESENTERIC GANGLION INNERVATING THE SMALL-INTESTINE OF THE CAT

Retrograde tracing was used to determine the localization of neuronal perikarya and fibres in the feline superior mesenteric ganglion (SMG), projecting to the small intestine. In the distal part of the ileum, a retrograde neuronal tracer Fast Blue (FB) was injected and after appr oximately thirty five to forty days the animals were killed by perfusi on. The SMG were removed and the neuropeptide contents of the neurons, projecting to the distal ileum, were determined by means of immunoflu orescence with antisera to neuropeptide Y (NPY), calcitonin gene-relat ed peptide (CORP), substance P (SP), somatostatin (SOM), and vasoactiv e intestinal polypeptide (VIP). Neurons innervating the small intestin e were located in the upper part of the SMG and all of them were NPY-i mmunopositive. The group of CGRP-immunoreactive (IR) cells was less nu merous (73.33%). Probably the FB-labeled fibres, containing the same n europeptides, arise from these perikarya. SP-or VIP-immunopositive neu ronal processes were found to surround immunonegative ganglionic cells but their origin is not in the ganglion. Only single FB-marked cells were VIP-immunopositive. SP-and SOM-immunoreactive amounted respective ly to 2.28% and 3.01% of all the neuronal population, but only a few o f these cells were FB-labelled.