Beta-adrenergic blockade in ponies with recurrent obstructive pulmonary disease

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Abstract
Ponies with recurrent airway obstruction have hyperresponsive airways during acute disease exacerbations but not during clinical remission. We examined the effect of .beta.-adrenergic blockade with propranolol on airway responsiveness to aerosol histamine in six ponies with recurrent airway obstruction and six age- and gender-matched controls. Measurements were made with principal ponies in clinical remission (period A) and during an acute period of airway obstruction (period B). .beta.-Adrenergic blockade did not change airway responsiveness, dynamic compliance (Cdyn), or pulmonary resistance (RL) in either group of ponies at period A or in the control ponies at period B. In principal ponies at period B, propranolol significantly increased RL but was without effect on Cdyn or airway responsiveness. We conclude that the .beta.-adrenergic system is involved in the control of central airway caliber in principal ponies at period B but that this system does not seem to be invovled in the mechanism of airway hyperresponsiveness to histamine.