Nedocromil sodium inhibits substance P‐induced potentiation of cholinergic neural responses in the isolated innervated rabbit trachea

Abstract

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 less than 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.