RESUMEN
The pulmonary depressor chemoreflex has been shown to be elicited to be elicited by stimulation of pulmonary C-fiber receptors. By using a preparation in which the left pulmonary was ligated and cannulated and in which the right and left lungs were ventilated separately, the reflex responses of cardiovascular parameters to left pulmonary arterial (LPA) injection of C-fiber receptor agonist capsaicin and left lung inflation (LLI) were studied in open-chest dogs. LPA injection of capsaicin (up to 300 ตg) and LLI (30 cm H2O) caused transient hypotension and bradycardia. Left ventricular dP/dt at 30 mm Hg developed pressure and hind limb vascular resistance were also significantly reduced. These various responses were abolished by left cervical and hilar vagotomy. LPA injection of prostaglandin precursor arachidonic acid elicited dose-related hypotension and bradycardia which were likewise abolished by left hilar vagotomy. This study therefore demonstrates that chemical or mechanical stimulation of pulmonary afferents reflex decreases cardiovascular functions. Further, although the influence of mechanoreceptors cannot be excluded, this decrease in likely mediated by chemoreceptor.