EFFECT OF GANGLIONIC BLOCKADE ON BRONCHIAL REACTIVITY IN ATOPIC SUBJECTS

Abstract

To determine the site in the parasympathetic pathway responsible for the increased bronchial reactivity in 5 atopic subjects, the effect of premedication with aerosols of hexamethonium, a ganglionic blocking agent, and atropine, a postganglionic blocking agent, on the bronchomotor responses to histamine and methacholine aerosols was studied. After 7 mg of aerosolized atropine, baseline specific airway resistance (SRaw) decreased, and the increase in SRaw produced by histami ne and by methacholine were prevented in each subject (P < 0.001). After 1 g of hexamethonium, baseline SRaw was decreased to a similar level and the increase in SRaw produced by histamine was again prevented in each subject ( P < 0.001). The increase in SRaw produced by methacholine was not affected significantly in 3 subjects (P > 0.5) and was increased or decreased only slightly in 2 subjects (P < 0.05). Bronchial hyperreactivity in atopic subjects may be due to a change in the ch aracteristics of the efferent parasympathetic pathway at a site distal to the ganglion possibly at the smooth muscle, and that bronchodilation due to atropine and hexamethonium cannot account for their effects on bronchomotor responses.