Role of beta adrenergic receptors in carotid body function of the goat.

Previous studies in anesthetized or decerebrate cats and rabbits and awake man have shown conflicting results regarding a potential role for beta-adrenergic receptors in carotid body function. Therefore, we sought to clarify the role of beta-adrenergic receptor activity in carotid body function by assessing: the ventilatory response to intravenous isoproterenol infusion in awake and anesthetized carotid body intact and carotid body denervated goats, the effect of propranolol on the ventilatory response to isocapnic hypoxemia, and carotid sinus nerve chemoreceptor discharge rate response to isoproterenol and hypoxia. Isoproterenol increased ventilation to a similar degree in carotid body intact and denervated awake and anesthetized goats. This ventilatory increase was blocked by propranolol. Propranolol did not alter the hypoxic ventilatory response. Although ventilation increased, carotid sinus nerve chemoreceptor discharge rate was not altered by isoproterenol infusion or bolus IV injection in anesthetized goats. Hypoxia did increase carotid sinus nerve discharge rate. In this study, beta-adrenergic stimulation of ventilation did not occur via the carotid body, and beta-adrenergic blockade did not affect the carotid body hypoxic ventilatory response. Therefore, we found no evidence of functional beta-adrenergic activity within the carotid body of the goat.