NEDOCROMIL SODIUM INHIBITS SUBSTANCE P-INDUCED POTENTIATION OF CHOLINERGIC NEURAL RESPONSES IN THE ISOLATED INNERVATED RABBIT TRACHEA

1 Sensory neuropeptides such as substance P may be implicated in the pathophysiology of asthma. 2 It has been proposed that nedocromil sodium may inhibit the effects of neuropeptides. 3 In this study, using an isolated innervated preparation of rabbit trachea, substance P, 10(-6) M, potentiated contractions induced by parasympathetic stimulation. The effect of substance P at the preganglionic site (307 +/- 38% of control, n = 5), was similar to that at the postganglionic site (307 +/- 61% of control, n = 5). 4 Nedocromil sodium, 10(-7) M, significantly inhibited the substance P-induced potentiation preganglionically (199 +/- 44%, n = 4, P < 0.05) but not postganglionically (356 +/- 118%, n = 4). 5 These results suggest that nedocromil sodium may modify neuropeptide action selectively at a preganglionic site and that this may contribute to its therapeutic efficacy.