Genetic factors in non-specific bronchial reactivity in rats

Two bronchoconstrictory agents, serotonin (5 HT) and carbachol, were investigated in different inbred rat strains in order to delineate possible factors influencing the bronchial reactivity. The challenge was given intravenously and a single dose was given to an individual animal. Inbred strains of rats differed significantly from each other in their reactivity to 5 HT and to carbachol. IC rats were good reactors to both 5 HT and carbachol. RA rats were intermediate reactors to both agents. OM/N rats had a good reaction to 5 HT, but showed only a minor bronchoconstriction after carbachol. BN and LE rats were poor reactors to both agents. The strain reactivities to the 2 provocation agents were not related. Breeding studies, using a good reactor, IC, and a poor reactor, DA strain, showed that the bronchial reactivity to 5 HT was inherited with a pattern that fitted with the autosomal recessive way of inheritance, high reactivity being recessive.