Simple, noninvasive method to measure the antibronchoconstrictor activity of drugs in conscious guinea pigs.

A simple, noninvasive method is described for measurement of the oral antibronchoconstrictor activity of drugs in conscious guinea pigs. The guinea pigs were placed in a head-out plethysmograph for measurement of tidal volume (VT), and a head chamber was used to deliver a hypercapnic gas mixture (10% CO2, 69% N2, 21% O2) and histamine aerosol (0.05% for 30 s). Inhalation of CO2 caused an increase in VT that was reduced (61 +/- 3%) by exposure to histamine. The histamine-induced reduction of VT was significantly (p less than 0.05) reduced 1 hr after oral administration with the bronchodilators albuterol (1 and 10 mg/kg) and aminophylline (100 mg/kg), the calcium antagonist nifedipine (30 mg/kg), and the antihistamine chlorpheniramine (0.5 mg/kg). These results demonstrate the oral antibronchoconstrictor activity of drugs in this model. The major advantages of this technique are that it is simple to operate, is noninvasive, and does not require anesthesia.