NITRIC-OXIDE SYNTHASE-CONTAINING, PEPTIDE-CONTAINING, AND ACETYLCHOLINESTERASE-POSITIVE NERVES IN THE CAT LOWER ESOPHAGUS

The innervation of the cat lower oesophagus, including the lower oesop hageal sphincter, was studied by enzyme histochemistry, immunohistoche mistry, and confocal microscopy. In the lower oesophageal sphincter, a nd at a level 2 cm above it, no apparent differences were seen in the nerve distribution pattern. Among the nerve populations studied, acety lcholinesterase (AChE)-positive nerves were the most abundant in both these regions. The density of AChE-positive nerves was particularly ma rked in the circular muscle layer. A rich supply of nitric oxide synth ase (NOS)-containing nerves was identified by using an antiserum again st neuronal NOS, or by enzyme histochemical staining for NADPH diaphor ase activity. Vasoactive intestinal peptide (VIP)-immunoreactive nerve s had a similar distribution pattern as NOS-immunoreactive nerves, and nerves displaying immunoreactivity for NOS and VIP often showed profi les coinciding with AChE-positive nerves. As judged by confocal micros copy, immunoreactivities for helospectin, pituitary adenylate cyclase- activating peptide (PACAP) and VIP, to a large extent were found in th e same nerves. At a level 7 cm above the lower oesophageal sphincter, the total nerve supply was less than in the sphincter itself and 2 cm above it. Immunoreactivity towards VIP, PACAP and helospectin was also found to co-exist with NOS and neuropeptide Y within the same nerve s tructures. It is concluded that there is an intricate innervation patt ern in the feline lower oesophagus reflecting the complexity in the re gulation of its motility.