Abstract
Regional differences of noradrenergic innervation and noradrenergic α2 receptor distribution in the submucous plexus of guinea-pig caecum, large intestine, and rectum were investigated with immunofluorescence confocal microscopy. In the caecal submucous plexus, three dimensional basket-like arrangements of small and bright dots of tyrosine hydroxylase-like immunoreactivity (TH-LIR) were observed, whereas noradrenergic α2A receptor-like immunoreactivity (NAR-LIR) was detected in somata. Both TH-LIR and NAR-LIR were localized in neuronal somata of the transverse colon. A few TH-LIR positive cell somata and many TH-LIR positive spots forming chains passing through ganglia and interganglionic nerve strands were observed, but no NAR-LIR were seen in the submucous plexus of the descending colon. There were a few TH-LIR positive somata and puncta, but no NAR-LIR were observed in the ascending colon and rectum. All of these observations show the distinct regional differences in noradrenergic innervation and noradrenergic α2A receptor distribution in the guinea-pig submucous plexus.
