In vitro responses of bronchial spirals and parenchymal strips from healthy and heartworm-infected dogs.

Bronchial spirals and pulmonary parenchymal strips from control (noninfected) and Dirofilaria immitis-infected dogs were tested for isometric contractile response to histamine and carbamylcholine. Responses of bronchial spirals from control dogs and from D immitis-positive groups did not differ in responses to histamine or carbamylcholine. Parenchymal strips from D immitis-positive dogs showed greater response to histamine than did those from controls; responses to carbamylcholine did not differ.