The effects of intranasal histamine challenge on eustachian tube function.

Eustachian tube (ET) function was evaluated bilaterally by use of the inflation-deflation and forced-response test before and after nasal challenge with various doses of histamine in five adult and 10 infant rhesus monkeys (Macaca mulatta). Of the 20 experiments conducted on the infant and juvenile monkeys, functional ET obstruction resulted in six ears after a dose of 0.5 mg of histamine, in 10 ears after a dose of 1 mg, and in four ears after a dose of 2 mg. In contrast, of the 10 experiments conducted on the adult monkeys, functional ET obstruction developed in two ears after a dose of 1 mg of histamine and in two ears after a dose of 4 mg. Six ears failed to respond at doses of 8 mg of histamine. The ET obstruction was characterized by increases in the values of the passive function parameters and an abolition of the ability to equilibrate applied middle ear pressures by muscular activity. ET obstruction was not observed in any ears after challenge with a saline control. The severity of the induced ET obstruction was lessened within 60 minutes after challenge. These data are similar to those reported for intranasal pollen challenges in sensitized rhesus monkeys and human volunteers and suggest that type I allergic reactions at the site of the nasopharyngeal mucosa disrupts the normal functioning of the ET by a mechanism potentially mediated by histamine release.