Role of prostaglandins in marihuana-induced bronchodilation

In vitro evidence suggests that physiological effects of marihuana may be mediated by prostaglandins via the stimulation of phospholipase A2. To verify if marihuana could act by this route in vivo, we tested the effects of acetylsalicylic and mefenamic acids, inhibitors of cyclooxygenase, on marihuana-induced bronchodilation and tachycardia. In 11 healthy volunteers, marihuana smoking (7 mg/kg, 1.7% delta 9-tetrahydrocannabinol) produced a significant increase in specific airway conductance (from 0.262 +/- 0.033 to 0.360 +/- 0.050 s-1 X cm H2O-1, mean +/- SE, p less than 0.01), forced expiratory volume in 1 s (4.02 +/- 0.22-4.27 +/- 0.25 liter, p less than 0.05) and heart rate (73.2 +/- 2.0-108.5 +/- 5.2 beats/min, p less than 0.001). In a second session, acetylsalicylic or mefenamic acid was taken for 30 h before marihuana smoking. No inhibition of marihuana-induced increase of specific airway conductance, forced expiratory volume in 1 s and heart rate was found. These findings suggest that the bronchodilation and the tachycardia induced by marihuana smoking in humans are not mediated by prostaglandins.