Non-myelinated vagal lung receptors and their reflex effects on respiration in rabbits.

The response characteristics of non-myelinated vagal lung receptors have been studied in the anaesthetized rabbit. The results indicate that the behaviour of these endings strongly resembles those found in cats and dogs and that they can be classified into 'pulmonary' 'bronchial' and 'pulmonary-bronchial' groups depending on their accessibility from either circulation. Experiments involving pericardial block with local anaesthetic to exclude responses from cardiac receptors and the use of sodium dithionite as a novel stimulus to 'pulmonary' endings alone, have shown that the predominant effect of these endings in the anaesthetized rabbit is to increase respiratory frequency. Reflex responses from 'bronchial' endings similar provided sufficient amount of the activating chemical was given.