The expression of the P2X(3) nucleotide receptor in embryonic day 14-18, postnatal day 1-14 and adult mouse sensory ganglia was examined using immunohistochemistry. Nearly all sensory neurons in dorsal root ganglia, trigeminal ganglia and nodose ganglia in embryos at embryonic day 14 expressed P2X(3) receptors, but after birth there was a gradual decline to about 50% of neurons showing positive immunostaining for P2X(3). In embryos there were only small neurons, while from postnatal day 7 both large and small neurons were present. Isolectin B(4) (IB(4))-positive neurons in dorsal, trigeminal and nodose ganglia did not appear until birth, but the numbers increased to about 50% by postnatal day 14 when a high proportion of IB(4)-positive neurons were also positively labelled for the P2X(3) receptor. About 10% of neurons in dorsal, trigeminal and nodose ganglia were positive for calcitonin gene-related peptide in embryos, nearly all of which stained for P2X(3) receptors. This increased postnatally to about 35-40% in adults, although only a few colocalised with P2X(3) receptors. Neurofilament 200 was expressed in about 50% of neurons in trigeminal ganglia in the embryo, and this level persisted postnatally. All neurofilament 200-positive neurons stained for P2X(3) in embryonic dorsal root ganglia, trigeminal ganglia and nodose ganglia, but by adulthood this was significantly reduced. The neurons that were positive for calbindin in embryonic dorsal, trigeminal and nodose ganglia showed colocalisation with P2X(3) receptors, but few showed colocalisation postnatally.
Summary. NADPH-diaphorase activity together with nitric oxide synthase-and vasoactive intestinal polypeptide-immunoreactivities were examined in the neurons of the rat pancreas in culture. Nitric oxide synthase (NOS)-and vasoactive intestinal polypeptide (VIP)-immunoreactivities were localized in a subpopulation of neurons which were also NADPH-diaphorase positive. All neurons expressing colocalized activities for NOS/ VIP and NADPH-diaphorase were solitary cells in culture. Each of these double-labelled neurons was characterized by a round or oval cell body, with short and long processes emanating from it. Some of these processes traversed several micrometres before terminating on the exocrine acinar and endocrine cells. The present study provides evidence that nitric oxide may act as a regulatory agent in the inhibitory neural control of the secretory functions in the pancreas, thereby maintaining the milieu interieur of the organism.
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