The response of rapidly adapting pulmonary stretch receptors elicited by sodium cyanide is augmented by vagotomy in the rabbit

Abstract

Listen

Translate article

The responses of rapidly adapting pulmonary stretch receptor (RAR) activity, tidal volume ( V T), inspiratory airflow ( V I), transpulmonary pressure ( P trans) and dynamic lung compliance ( C dyn) to administration of NaCN (20 and 40 μg/kg) were compared before and after vagal section in anesthetized, spontaneously breathing rabbits. The responses of RARs were recorded from a partially dissected branch of the left vagus nerve (LVN). Before vagal section, hyperpnea following NaCN administration led to increases in RAR activity, V T, V I and P trans, but caused a decrease in C dyn. Those responses obtained became more prominent by increasing the dose of NaCN. Under these conditions the increased receptor activity fired throughout the whole respiratory cycle. The responses of RAR activity, V T and P trans to NaCN administration were augmented by a vagal section that was produced by denervating the rest of the LVN still intact and right vagus nerve, and the discharge of receptors showed a predominantly inspiratory pattern that corresponded to augmentation of both P trans and V T. Vagal section, however, had no significant effect on the changes of V I and C dyn induced by NaCN. In addition, mean percent changes of increased V T and P trans produced by NaCN administration after vagal section were similar to those before vagal section. Furthermore, augmentation of V T and elevation in baseline V T, when NaCN after bilateral vagotomy was administered i.v., were preceded by simultaneously increased P trans and RAR activity. These results suggest that augmentation of NaCN-induced RAR stimulation in animals without intact vagus nerves is related to concomitant changes in the respiratory mechanics such as P trans and V T, probably involving the increased sensitivity of receptors to these two factors.