Structural changes in tracheal nerves and muscle associated with in vivo sensitization of guinea pigs.

The ultrastructure of guinea-pig tracheal smooth muscle and its innervation were studied in control and antigen (ovalbumin) sensitized animals. There was a reduction in the frequency and in the proportion of membrane occupied by gap junctions in sensitized muscle. In addition, there was a decrease in the proportion of varicosities with small granular vesicles relative to other nerve varicosities and to the number of smooth muscle cells. Earlier functional studies in vitro (Mansour and Daniel, 1987) did not reveal altered function of adrenergic nerves or adrenoceptors concentration-response curves to a wide variety of agonists and showed few changes. These studies suggest that inflammatory mediators released during antigen-sensitization may regulate the density of gap junctions and influence nerve structure. These studies also suggest that procedures to evaluate directly cell-to-cell coupling and nerve function after sensitization are needed.