Non-adrenergic, non-cholinergic neurons innervating the guinea-pig trachea are located in the oesophagus: evidence from retrograde neuronal tracing

The possibility that non-adrenergic, non-cholinergic (NANC) neurons innervating the guinea-pig trachea may be located within the oesophagus has been investigated using an in vitro retrograde tracing technique. The cervical trachea and oesophagus were excised from guinea-pigs and DiI was applied to a 5 mm region of the trachealis muscle. These preparations were maintained in organotypic culture for 3 days and processed for immunohistochemistry. A mean of 44 (4 neural cell bodies in the oesophageal myenteric plexus were found to be labelled by DiI. The vast majority of these neurons contained nitric oxide synthase, vasoactive intestinal polypeptide and neuropeptide Y. It is suggested that the population of neurons identified in this study are postganglionic parasympathetic neurons mediating NANC relaxation of the trachealis muscle in this species. (C) 1998 Elsevier Science Ireland Ltd.