Analysis of the vagal reflex tracheal constriction in the dog.

Influence of Ouabain on the Tracheal Musculature of the Dog

“…infusion of ouabain, there was a differential tendency with respect to the total dose of ouabain be tween the appearance of tracheal constriction and bradycardia. In a previous report (12), we demonstrated that inhalation of histamine, over a range of concentrations from 0.000625-0.0025%, caused a vagal reflex induced tracheal constriction before there was a measurable change in blood pressure and heart rate. Although intracerebroventricular administration of histamine induced the vagal ly mediated tracheal constriction in guinea pigs (14) and dogs (15), there were no The change is significant at **P<0.01 when compared to the value of the control.…”

“…Several investigators have re ported the existence of afferent fibers in the recurrent laryngeal nerve (16)(17)(18). We found previously (12) that the reflex tracheal con striction is completely blocked by the com bination of a vagal blockade and sectioning of the superior laryngeal nerves, indicating that the extravagal pathway plays a role in some part of the afferent pathway of the vagal reflex responses of the airway. In the present study, therefore, the bilateral cervical vagus, superior laryngeal and recurrent laryngeal nerves were cut to effect a complete vagal blockade.…”

“…The bilateral vagotomy was performed by sectioning not only of the bilateral cervical vagus nerves but also the bilateral superior laryngeal and recurrent laryngeal nerves. In a previous report, we showed that a complete inhibition of vagal reflex-induced tracheal constriction was not observed with a bilateral vagal blockade alone (12). It is well-known that afferent fibers exist in the superior laryn geal nerve.…”

“…Ex periments were carried out with the prepara tion used for the evaluation of the vagal reflex induced responses of the airway, as described previously (12). Briefly, the cervical trachea was exposed and then transected at a site about 7 cm caudal to the larynx with the mem branous wall left intact.…”

“…Although the potentiating effect of cardiac glycosides on the efferent vagal activity in the heart is recognized as an established fact, there are few reports of investigations that relate to the airway. In the present study, we examined the effects of ouabain on the tracheal musculature of the dog, using this preparation to measure the vagal reflex-induced tracheal response, as described previously (12).…”