The response of rapidly adapting pulmonary stretch receptors elicited by sodium cyanide is augmented by vagotomy in the rabbit.
The responses of rapidly adapting pulmonary stretch receptor (RAR) activity, tidal volume (VT), inspiratory airflow (VI), transpulmonary pressure (Ptrans) and dynamic lung compliance (Cdyn) to administration of NaCN (20 and 40 micrograms/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, VT, VI and Ptrans, but caused a decrease in Cdyn. Those responses obtained became more prominent by increasing the does of NaCN. Under these conditions the increased receptor activity fired throughout the whole respiratory cycle. The responses of RAR activity, VT and Ptrans 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 Ptrans and VT. Vagal section, however, had no significant effect on the changes of VI and Cdyn induced by NaCN. In addition, mean percent changes of increased VT and Ptrans produced by NaCN administration after vagal section were similar to those before vagal section. Furthermore, augmentation of VT and elevation in baseline VT, when NaCN after bilateral vagotomy was administered i.v., were preceded by simultaneously increased Ptrans 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 Ptrans and VT, probably involving the increased sensitivity of receptors to these two factors.
Matsumoto
S
S
Department of Physiology, Fukushima Medical College, Japan.
Shimizu
T
T
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D008297:Male; D011661:Pulmonary Stretch Receptors / Q000187:drug effects*; D012123:Pulmonary Ventilation / Q000187:drug effects; D011817:Rabbits; D012966:Sodium Cyanide / Q000494:pharmacology*; D013990:Tidal Volume / Q000187:drug effects; D013997:Time Factors; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology
D012966:Sodium Cyanide