CHEMICAL CODING OF NEURONS THAT PROJECT FROM DIFFERENT REGIONS OF INTESTINE TO THE CELIAC GANGLION OF THE GUINEA-PIG

The chemical codings of neurons that project from the small intestine, caecum, proximal colon, distal colon and rectum to the coeliac gangli on of the guinea pig were investigated. The coeliac ganglion was injec ted with the retrogradely transported dye Fast Blue, and each of the r egions was examined 6 days later in wholemounts that had been prepared for immunohistochemical localisation of pairs of antigens. In both th e small and large intestines, all intestinofugal neurons were immunore active (IR) for choline acetyltransferase (ChAT). In each region of th e large intestine, the largest population, representing 50-60% of retr ogradely labelled neurons in each region, was immunoreactive for ChAT, bombesin (BN), calbindin (Calb) and nitric oxide synthase (NOS). Most intestinofugal neurons in the small intestine contain bombesin and VI P-IR along with ChAT-IR but none contain either Calb or NOS. Thus, ner ve endings of enteric origin in the coeliac ganglion that contain NOS- IR or Calb-IR come from the large intestine and those with bombesin-IR but not NOS-IR are from the small intestine. The gastric wall was inj ected with Fast Blue in order to label noradrenegic (NA) neurons in th e coeliac ganglion and to determine, by localisation of NOS and bombes in-IR, whether they receive inputs from the small and large intestine. Some NA neurons received inputs from the large intestine (and perhaps also from the small intestine) and some received inputs exclusively f rom the small intestine. Most NA neurons that received intestinofugal inputs had the chemical code NA/-; some were immunoreactive for somato statin (NA/SOM neurons), but those with IR for neuropeptide Y (NA/NPY) rarely received intestinofugal inputs.