Morphology of cough receptor nerve terminals in the guinea pig trachea. Presumed cough receptor nerve terminals labeled (A) with the vital styryl dye FM2-10 and (B) immunohistochemically for α3 Na+/K+ ATPase. Note the terminal structures are arranged parallel to the tracheal muscle fibers (running from top to bottom of the panels). The cough receptor terminals (A, B) are clearly differentiated from substance P-containing (SP) tracheal nociceptors (C). The arrow heads and small arrows in panels (A) and (B) illustrate individual cough receptor axons and the nerve bundles from which the axons arise, respectively. The asterisk in panel (C) shows the origin of a primary bronchus at the caudal end of the trachea. The scale bar represents 200 μm in panel (A) and 50 μm in panels (B) and (C). These images were generated, but not used for publication, during previous studies (FM2-10 staining from reference  and α3 Na+/K+ ATPase/SP immunohistochemistry from reference ). Refer to [6, 9] for detailed methods.