NADPH-DIAPHORASE-POSITIVE NERVE-FIBERS ASSOCIATED WITH MOTOR END-PLATES IN THE RAT ESOPHAGUS - NEW EVIDENCE FOR CO-INNERVATION OF STRIATED-MUSCLE BY ENTERIC NEURONS

NADPH-diaphorase histochemistry was combined with demonstration of ace tylcholinesterase and immunocytochemistry for calcitonin gene-related peptide to study esophageal innervation in the rat. Most of the myente ric neurons stained positively for NADPH-diaphorase, as did numerous v aricose nerve fibers in the myenteric plexus, among striated muscle fi bers, around arterial blood vessels, and in the muscularis mucosae. A majority of motor endplates (as demonstrated by acetylcholinesterase h istochemistry or calcitonin gene-related peptide immunocytochemistry) were associated with fine varicose NADPH-diaphorase-positive nerve fib ers. Analysis of brainstem nuclei, sensory vagal, spinal, and sympathe tic ganglia in normal and neonatally capsaicin-treated rats, and compa rison with anterogradely labeled vagal branchiomotor, preganglionic an d sensory fibers led to the conclusion that NADPH-diaphorase-positive fibers on motor endplates originate in esophageal myenteric neurons. N o association of NADPH-diaphorase-positive nerve fibers with motor end plates was found in other organs containing striated muscle. These res ults suggest extensive, presumably nitrergic, co-innervation of esopha geal striated muscle fibers by enteric neurons. Thus, control of peris talsis in the esophagus of the rat may be more complex than hitherto a ssumed.