We have developed a guinea pig model that allows monitoring of single
afferent nerve fiber activity after stimulation of tracheal nerve endi
ngs with various stimuli. Action potentials from nodose or jugular neu
rons are recorded extracellularly. Previous experiments have shown tha
t the excitability of the nerve endings to, for example, mechanical st
imuli can be increased by antigen challenge of presensitized guinea pi
gs. Nedocromil sodium 10(-4) mol/L significantly reduced by more than
50% the generation of action potentials in C fibers in response to sti
mulation by capsaicin. The precise mechanism is not known, although th
e membrane depolarization induced by capsaicin was reduced in the pres
ence of nedocromil sodium. This agent did not have a generalized inhib
itory effect on afferent excitability because it had no effect on sens
itivity to electrical or mechanical stimuli. Nedocromil sodium did not
affect the generation of action potentials in A delta and C fibers in
the presence of hypertonic saline solution.