BRONCHO-AND VASO-MOTOR RESPONSES OF GUINEA-PIG LUNGS

¹ Physiology Department, University of Edinburgh

In isolated perfused lungs of the guinea-pig perfused with recirculating Ringer-Locke solution:

1. Acetylcholine raises the intrapulmonary pressure and diminishes the venous outflow, both effects being abolished by atropine.

2. Adrenaline frequently produces a fall in intrapulmonary pressure together with an increase in venous outflow. When no change in intrapulmonary pressure occurs a fall in venous outflow takes place. These results confirm those of Dale and Narayana. In addition it has been found that adrenaline may cause under certain conditions a slight but definite rise in intrapulmonary pressure; the latter phenome-non may possibly depend upon the retention in the circulating perfusate of substances diffusing out from the lung tissues. It was found that ergotoxine converts this adrenaline intrapulmonary rise to a fall.

3. Stimulation of the peripheral end of the cut cervical vagosympathetic nerves usually causes a rise in intrapulmonary pressure associated with a diminution or no change in outflow.

4. Stimulation of the peripheral ends of the cut cervical sympathetic nerves produced a rise in intrapulmonary pressure without any associated change in the venous outflow in one experiment. In three experiments on ergotoxinised animals a fall in intrapulmonary pressure took place, again without any significant venous outflow change.

5. Stimulation of the peripheral ends of the cervical vagi leads to a rise in intrapulmonary pressure together with a diminution or no change in the venous outflow.

6. Ergotoxine reverses the bronchoconstriction produced by stimulation of the cervical vagi or cervical vagosympathetic nerves.

7. Examination of variations in the venous outflow and intra-pulmonary pressure, whether spontaneous or due to nerve stimulations or drug administrations, shows that the venous outflow alterations are not always dependent upon bronchomotor effects.

The expenses of this research were defrayed by a grant from the Moray Endowment Committee, for which I wish to express my thanks.