Expiratory effects of brief carotid sinus nerve and carotid body stimulations.

The expiratory response, measured directly as ventilatory volume and as internal intercostal or abdominal muscle EMG activity, to brief intermittent electrical stimulation of the carotid sinus nerve or chemical stimulation of the carotid body was determined in anesthetized cats. Stimuli given during expiration had a specific expiratory effect, manifested by increased expiratory duration, increased activity of expiratory muscles and increased depth of expiration. The later in expiration the stimulus was exhibited, the greater all effects became. Vagal section had no effect on the response and the duration of response persisted after spinal cord section at C7-T1. It is concluded that expiratory stimulations have effects on expiration similar to those on inspiration from stimulations given during inspiration. It is concluded that the mechanism operates at a brain stem level. However, because the latency of the response is much longer than the inspiratory response to the same stimuli, the pathway must be different.