Antigen enhances neuronally induced contraction of intrapulmonary bronchi from IgE-producing rabbits

The effect of in vitro antigen exposure on contraction induced by electrical field stimulation (EFS) was examined in bronchial rings isolated from rabbits producing specific IgE antibodies. After exposure to antigen, tissues showed an enhanced isometric contractile response to EFS especially at low frequencies, leading to a significant change in the mean slope factor (p<0.05) derived from modeling the log frequency response curve using a 4-parameter logistic function. Also, the mean log EF20±SEM decreased from 1.03±0.05 to 0.88±0.07 Hz (p<0.02). This antigen-induced effect was blocked by pretreatment with 3μM chlorpheniramine and not observed in unsensitized tissues. Antigen challenge of tissues passively sensitized with IgE (but not IgG) antibodies led to a similar EFS-enhancing effect, significantly reducing the mean slope factor (p<0.025). Substituting EFS with exogenous acetylcholine resulted in no antigen-induced enhancement of contraction. The data suggest that antigen-IgE interaction leads to local histamine release sufficient to enhance the function of excitatory airway neurons.