Adrenergic Blockade Does not Change Ventilatory Response to CO2 in Awake Resting Goats

摘要

Although adrengenric agonists increase resting ventilation and responsiveness to carbon dioxide, there are conflicting data about the effect of adrenergenic blockade on ventilatory responses. In this study, we investigated the effect of alpha- or beta-adrerengenic blockade on the response to hyperoxic CO2 rebreathing in awake goats. In five goats, studied before and after intravenous administration of phentolamine or propranolo, there was no difference (compared to control studies) in the mean slope, x-intercept, or ventilation at end-tidal PC02 (PEYCO2) = 70 torr for the CO2 repsonse curves after either drug. When mean insporatory flow rate was plotted against PETCO2, there was also no change in these measurements after propranolol. After phentolamine, there was a slight decrease in the slope and x-intercept, but no change in inspiratory flow rate at PETCO2 = 70. We conclude that acute administation of alpha- or beta-adrerengenic blockers does not affect ventilatory repsonse to CO2 inhalation in goats, and suggest that adreregenic activity is not an important modulating influence for CO2 responsiveness in this species.