Abstract
The present investigation was conducted in an effort to demonstrate the attenuating effect of an alpha-adrenergic blocking agent (phenoxybenzamine) on the contraction of guinea pig trachea (GPT) with various bronchoconstrictors.
Male guinea pigs weighing 250-300g, were killed. Guinea pig tracheas were removed, suspended in bioassay glass jackets and superfused with Krebs-Henseleit solution at 37°C saturated with oxygen and carbon dioxide (95:5, v/v). Contraction of guinea pig trachea was detected by an isotonic transducer and displayed on a polyrecorder.
1) The contractile responses of guinea pig trachea with acetylcholine and serotonin decreased with continuous infusion of phenoxybenzamine, and continued to decrease with increasing doses of phenoxybenzamine.
2) The dose-response curves of acetylcholine, histamine, serotonin, bradykinin and prostaglandin F2α in guinea pig trachea were lowered with continuous infusion of phenoxybenzamine.
3) These results may suggest that an alpha-adrenergic blocking agent (phenoxybenzamine) has an attenuating effect on bronchoconstrictors, in addition to potentiating effect on bronchodilators.
