A retrograde labeling technique for the functional study of airway-specific visceral afferent neurons

The development of a method is described whereby primary afferent neurons that specifically innervate the airways in the guinea pig can be retrogradely labeled, acutely dissociated and studied functionally with electrophysiological techniques. Following administration of either dextran-tetramethylrhodamine, Fast Blue, or Fluorogold dye into the tracheal lumen, dye-labeled neurons can be visualized in 100 microns serial nodose ganglion sections. Control experiments show that labeling does not result from the undesirable spread of the dyes to target innervation fields in the gastrointestinal (GI) or cardiovascular (CV) systems. Neuronal somata retain dye label when acutely dissociated. Microelectrode studies provide evidence that the presence of the Rhodamine dye label and its fluorescent excitation neither alter basic electrophysiological membrane parameters nor the chemoreceptive properties of isolated neurons. Thus this new method will allow the isolation of individual airway-specific primary visceral afferent neurons for functional studies with multidisciplinary techniques.