Nitrergic neurons in the pancreas of newborn guinea pig: their distribution and colocalization with various neuropeptides and dopamine-beta-hydroxylase.

The distribution of nitrergic neurons in the pancreas of the newborn guinea pig was first investigated, using nitric oxide synthase (NOS) immunofluorescence and nicotinamide adenine dinucleotide hydrogen phosphate-diaphorase (NADPH-d) histochemistry. There was total colocalization of NOS and NADPH-d in the pancreatic ganglion cells. NADPH-d was then used as a marker for NOS. In the whole mount preparation of the pancreas, most of the nitrergic neurons were located in the head and the body region, along the branches of pancreatic blood vessels. Some were also associated with the main pancreatic duct, islets of Langerhans and pancreatic acini. To investigate whether NADPH-d stained cells were neurons and whether NADPH-d was colocalized with various neuropeptides and dopamine-beta-hydroxylase (D beta H), an enzyme involved in the synthesis of noradrenaline, antibodies against neuron specific enolase (NSE), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY). D beta H, substance P (SP), calcitonin gene-related peptide (CGRP) and bombesin (BOM) were used. Of all NSE positive ganglion cells, 76.8% were NADPH-d positive. NOS, VIP, NPY and D beta H immunoreactivities were found in both the neuronal cell bodies and nerve fibres in the pancreas while SP, CGRP and BOM immunoreactivities were detected only in the nerve fibres. SP-, CGRP- and BOM-containing nerves were in close contact with both NADPH-d positive as well as NADPH-d negative neurons. The percentages of NADPH-d/VIP, NADPH-d/NPY, NADPH-d/D beta H neurons in the total number of pancreatic neurons were 67.4%, 53.5%, 21.5% respectively. With double labelling in adjacent sections three subpopulations of pancreatic ganglion cells were demonstrated: NADPH-d/VIP/NPY, NADPH-d/VIP/D beta H and NADPH-d/NPY/D beta H.