Observations on carotid body chemoreceptor activity and cervical sympathetic discharge in the cat.

1. Parallel recordings have been made of the cervical sympathetic and carotid body chemoreceptor activity in the anaesthetized cat.2. The sympathetic activity remains remarkably constant while the chemoreceptor activity is varied by changes in the blood gas tensions of relatively short duration.3. Changes in intrathoracic pressure by obstruction to the airway or thoracic compression were associated with changes in the activity of both nerves.4. It is likely that, under normal conditions, the sympathetic nervous activity provides a stable vasomotor tone within the carotid body.