Ventilatory Response to CO2 Rebreathing After Adrenergic Blockade in Goats,
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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Administration of adrenergic agonists enhances resting ventilation and increases responsiveness to C02 inhalation, though there are conflicting data about the effect of adrenergic blockade on ventilatory responses. In this study, we investigated the effect of alpha- or beta-adrenergic blockade on the ventilatory response to hyperoxic C02 rebreathing in awake goats. Five goats were studied before and after intravenous administration of phentolamine 3.8 mg bolus followed by 0.19 mgmin or propranolol 0.15 mgkg. Adequacy of alpha- or beta-adrenergc blockade was subsequently demonstrated by assessing the pressor response to norepinephrine or the heart rate response to isoproterenol, respectively. There was no difference compared to control studies in the mean slope, x-intercept, or ventilation at end-tidal PC02 70 torr for the C02 response curves after the goats had received either phentolamine or propranolol. When mean inspiratory flow rate VTTi was plotted against end-tidal PCO2, there was also no change in slope x-intercept or VTTi at end-tidal PCO2 70 torr after the goats had received propranolol.