Effect of histamine on the airway smooth muscle of cats under control and inflammatory conditions.

Previous in vitro studies on airway smooth muscles of cats with turpentine oil-induced inflammation of the airways have shown an increased sensitivity of the lung strips to histamine application. This effect was abolished by pretreatment with phentolamine. This communication describes the effect of prazosin and yohimbine on histamine responsiveness of strips of control and inflamed lungs. Prazosin had no effect on histamine-induced contraction of the control lung strips. However, the histamine-induced contraction of the experimental strips was depressed. Yohimbine depressed histamine-induced tension even in control lung strips. The role of alpha 1-adrenergic receptors in the increased responsiveness of the inflamed lung tissues to histamine is discussed.