Eye, Ear, Nose &throat Monthly a Practical Journal for the Eye, Ear, Nose and Throat Specialist

The striking success of antihistaminic agents such as pyribenzamine, benadryl and several others in controling the nasal turgescence and rhinorrhea of seasonal hay fever, and in relieving the symptoms of urticaria, led to exaggerated hopes of similar results in the treatment of asthma. While the effectiveness of antihistaminic agents has lent considerable support to the role of histamine in allergy, it may also tend to overemphasize the histamine side. In asthma pyribenzamine apparently fails to dilate the bronchioles thus giving little or no comfort to the patient. This would suggest that normal bronchiolar tone is the result of an active balance between the constricting action of histamine and the dilating capacity of epinephrin. In a previous publication I described the experimental microscopic observation of bronchiolar reaction to histamine and the antihistamine effect of Vitamin C. In this experiment the lung of the white New Zealand rabbit was filled with gelatin and then excised and kept viable in Ringer-LockeGlucose solution. After chilling, the lung was cut so that each section contained a bronchiole. This was mounted on a small ring so that it could be observed under the microscope. The gelatin was now washed out of the lung tissue and the whole preparation was maintained viable in the Ringer-LockeGlucose solution at a fixed temperature. When histamine was added to the solution, the bronchiole promptly contracted and the change of size was drawn through the camera lucida and calculated by means of the planimeter. After the addition of Vitamin C, the bronchiole recovered from the contractions and became moderately dilated. If epinephrine was added the dilatation would increase further. [For the exact technique reference may be made to the original article.] At the time of the reporting of this experiment I interpreted the dilatation of the bronchiole after the histamine contraction as attributable to the antihistamine action of Vitamin C. In the light of subsequent study I am inclined to believe that the counteraction of the histamine contraction was due, not to the chemical neutralization of histamine, but rather to the potentiation of the epinephrin already present in the viable section of bronchiole. This explanation became even more probable from the demonstration that, if additional epinephrin was added, the bronchiole dilated to twice the size of the normal bronchiole before the histamine had been added, thus showing that a very active dilator effect was produced.