Effect of topically applied atropine, methysergide and chlorpheniramine on nasal challenge with serotonin.

Serotonin challenge in the nose produces sneezing and rhinorrhoea. To study the mode of action of serotonin in the nose, 14 normal persons, in a double-blind, randomized study, were provoked with serotonin in three concentrations. Fifteen minutes before challenge, they were pretreated in the nose with either a cholinoceptor antagonist (atropine), a serotonin antagonist (methysergide), an H1-histamine antagonist (chlorpheniramine) or isotonic saline. The number of sneezes was noted, and the amount of secretions measured. Serotonin induced dose-related increase in sneezing and hypersecretion (P less than 0.02). Atropine pretreatment reduced the amount of secretion (P less than 0.05 and P less than 0.1), but had no effect on sneezing. Methysergide and chlorpheniramine had no effect on the serotonin-induced nasal symptoms. Unilateral challenge with serotonin induced secretions from both sides, suggesting that serotonin-induced nasal symptoms are partly reflex-mediated.