CHANGES IN ACTIVITY OF PULMONARY RECEPTORS IN ANAESTHESIA AND THEIR INFLUENCE ON RESPIRATORY BEHAVIOUR

¹ From The Departments of Physiology and Pharmacology, Oxford

1. The effect of anaesthetics on the pulmonary afferent nerve endings has been investigated by recording action potentials in vagal single fibre preparations.

2. All volatile anaesthetics tested caused an increase in the sensitivity of stretch receptors. This occurred in spinal cats ventilated artificially with constant volumes of air, and also in decerebrate cats breathing spontaneously.

3. Cyclopropane and nitrous oxide caused hyperexcitability of stretch endings throughout exposure. Ethylchloride, chloroform, divinylether, ethyl ether and trichlorethylene caused stimulation followed by paralysis. Chloralose and nembutal caused no stimulation and but showed some depression in large doses.

4. The activity of deflation endings was studied in rabbits by selective blocking of the vagal fibres and recording from a diaphagm slip preparation.

5. Those deflation endings which produce acceleration of respiration in the rabbit, were first stimulated and then paralysed by ether, whereas trichlorethylene caused prolonged stimulation.

6. The interaction of these effects on stretch endings and on deflation endings, and the extent to which they determine the respiratory behaviour in the intact animal is discussed.