[Spike activity of the pulmonary stretch receptors of cats with pneumothorax]

In 24 anesthetized and vagotomized cats, activity on high-threshold as well as 45% of low threshold and intermediate receptors during collapse of lungs either decreased essentially or stopped altogether. In other 55% of low-threshold and intermediate receptors the decrease of firing rate during expiration was either weak or absent, although a decrease in respiratory modulations of firing rate did occur. In great pneumothorax (100--120 ml) these receptors discharged evenly with the frequency 4 to 40/sec. The data obtained corroborate the hypothesis suggesting that the low-frequency impulse activity of the lung stretch receptors induces stimulation of inspiration and shortens the expiration.