Neither axotomy nor target-tissue inflammation changes the NOS- or VIP-synthesis rate in distal bowel-projecting neurons of the porcine inferior mesenteric ganglion (IMG).

The present study was aimed at disclosing axotomy- and inflammation-induced changes in the chemical coding of retrogradely labelled distal bowel-projecting neurons in the porcine IMG. Particular attention was paid to the changes in the expression pattern of vasoactive intestinal polypeptide and nitric oxide synthase (as a marker of nitric oxide) in affected cells, as these substances are thought to play a crucial role in the regeneration of injured sympathetic neurons. However, while both pathological processes failed to induce an increase in the number of sympathetic bowel-projecting neurons exhibiting vasoactive intestinal polypeptide or nitric oxide synthase, axotomy, but not target-tissue inflammation, led to the upregulation in the expression pattern of galanin, pituitary adenylate cyclase-activating peptide and/or Leu5-enkephalin in the affected perikarya. On the other hand, axotomy resulted in a diminished density of vasoactive intestinal polypeptide-immunoreactive intraganglionic nerve fibres, whilst target-tissue inflammation evoked a distinct increase in the number of visible vasoactive intestinal polypeptide-immunoreactive terminals, especially in those regions where bowel-projecting neurons were located. Thus, the data obtained in the present study run counter to the results of the injury-related responses observed in neurons of the sympathetic chain ganglia, suggesting the existence of either species- or target tissue-dependent differences in the injury-induced responses of the affected sympathetic neurons.