Photograph of the experimental preparation used to study the electrophysiology of jugular and nodose afferent nerves with receptive fields within the central airway or right lung. (A) The trachea and bronchi are opened along a midline ventral incision, pinned lumen-side-up and vagal ganglia are isolated in a separate chamber for recording. Excess tissue is left on the edges of the ganglia to secure the ganglion firmly with minute pins to the Sylgard-lined dish. (B) The trachea and pulmonary artery are cannulated (arrowheads), allowing for perfusion with 37°C oxygenated Krebs bicarbonate solution. The arrows point to the jugular and nodose ganglia in the recording chamber. The ganglia are pinned to the chamber floor as in (A) and an extracellular recording electrode is placed in the nodose ganglion. The Xs and Os represent the approximate location at which a punctate mechanical stimulus with a von Frey probe (B) evoked a discharge of action potentials in a given jugular (O) or nodose (X) C-fiber. (C) Representative extracellular recordings of action potential discharge from nodose and jugular C-fibers with receptive fields within the right lung (as in B). The arrow denotes the point at which 1 ml of ATP (30 µM), -methylene-ATP (30 µM), or capsaicin (0.3 µM) was infused into the trachea or pulmonary artery. The top tracing is from a nodose C-fiber with a receptive field in the middle lobe of the right lung. The bottom tracing is from a jugular C-fiber with its receptive field in the middle lobe of the right lung. Note that the jugular C-fiber is unresponsive to ATP, but is stimulated by capsaicin. By contrast, the nodose C-fiber responds vigorously to ATP. This ATP effect is mimicked by the P2X receptor selective agonist ,-methylene-ATP (from Undem et al., 2004).