REGIONALLY DIFFERENT NORADRENERGIC INNERVATION AND RECEPTOR DISTRIBUTION IN SUBMUCOUS PLEXUS OF GUINEA-PIG INTESTINE

Regional differences of noradrenergic innervation and noradrenergic al pha 2 receptor distribution in the submucous plexus of guinea-pig caec um, large intestine, and rectum were investigated with immunofluoresce nce confocal microscopy. In the caecal submucous plexus, three dimensi onal basket-like arrangements of small and bright dots of tyrosine hyd roxylase-like immunoreactivity (TH-LIR) were observed, whereas noradre nergic alpha 2A receptor-like immunoreactivity (NAR-LIR) was detected in somata. Both TH-LIR and NAR-LIR were localized in neuronal somata o f the transverse colon. A few TH-LIR positive cell somata and many TH- LIR positive spots forming chains passing through ganglia and intergan glionic nerve strands were observed, but no NAR-LIR were seen in the s ubmucous plexus of the descending colon. There were a few TH-LIR posit ive somata and puncta, but no NAR-LIR were observed in the ascending c olon and rectum. All of these observations show the distinct regional differences in noradrenergic innervation and noradrenergic alpha 2A re ceptor distribution in the guinea-pig submucous plexus.