A COMPARISON OF SENSORY NERVE FUNCTION IN HUMAN, GUINEA-PIG, RABBIT AND MARMOSET AIRWAYS

We have investigated the role of sensory nerves in regulating airway s mooth muscle function in the guinea-pig, marmoset, rabbit and man. Tis sue levels of the sensory neuropeptides CGRP and substance P in the ai rways of the guinea-pig were significantly greater compared with the r abbit and marmoset. The relative order of tissue content was guinea-pi g >>> rabbit = marmoset. Marmoset bronchial and tracheal preparations responded weakly to exogenously administered substance P and neurokini n A but contracted to methacholine and demonstrated atropine-sensitive cholinergic responses. In marmoset, rabbit and human airway preparati ons, capsaicin mediated weak contractile responses to exogenously admi nistered capsaicin. However, high concentrations of capsaicin elicited a relaxation response that was epithelium-independent, cyclo-oxygenas e-insensitive, not involving nitric oxide and not dependent on the act ivation of capsaicin-sensitive afferents. These results suggest that r abbit and marmoset airways respond functionally in a similar way to hu man airway preparations and maybe more relevant than guinea-pig airway s with regard to understanding the role of sensory neuropeptides in ai rways.