Characterization of excitatory and inhibitory motor neurons to the human gastric clasp and sling fibers.

The aim of this study was to determine the morphology and position of the excitatory and inhibitory motor neurons to the human gastric sling and clasp fibers. Motor neurons were identified by retrograde staining with 1,1'-didodecyl 3,3,3',3'-indocarbocyanine perchlorate (DiI), and choline acetyltransferase (ChAT) or nitric oxide synthase (NOS) immunoreactivity was then determined in these motor neurons. In the sling preparations, 46% of the DiI-stained cells were aboral motor neurons, 43% were local motor neurons, and only 10% were descending motor neurons. Overall, 58% were immunoreactive for ChAT, and 36% for NOS (P = 0.042). Sixty-two percent of local, and 66% of aboral DiI-stained motor neurons were immunoreactive for ChAT. In the clasp preparations, 52% of the DiI-stained cells were descending motor neurons, 45% were local motor neurons, and only 3% were aboral neurons. Overall, 31% were immunoreactive for ChAT and 65% for NOS (P = 0.039). Eighty-five percent of the DiI-stained descending motor neurons were immunoreactive for NOS. All of the cells that were labeled adequately had a single axon and a number of filamentous or flattened lobular dendrites, and fitted into the broad category of Dogiel type I neurons. In conclusion, the majority of the motor neurons to the sling fibers were ChAT-positive excitatory neurons from the myenteric plexus of the stomach and the local region, and to the clasp were predominantly NOS-positive inhibitory neurons from the esophagus.