Adrenergic and cholinergic responses of the tracheal smooth muscle is enhanced during estrus phase in rat

Materials and methods: The study was performed in 5 groups of rat tracheal smooth muscle obtained during proestrus, estrus, metestrus, and diestrus phases of the estrous cycle, as well as the ovariectomized group (n:8/group). Cumulative acetylcholine contractions ranging from 10 to 10 M bath doses and the cumulative isoproterenol relaxations ranging from 10 to 10 M precontracted with 10 M of acetylcholine were recorded on isolated tracheas placed in a computerized tissue bath system. Results: Acetylcholine-induced contractions ranging from 10 to 10 M were significantly enhanced dose-dependently in tracheal smooth muscle from estrus rats compared to those from metestrus and ovariectomized rats. The relaxation induced by isoproterenol (10-10 M) also significantly increased in tracheal smooth muscle precontracted with acetylcholine (10 M) taken from estrus rats. However, acetylcholine-induced contractility increase in tracheal smooth muscle was much more prominent than isoproterenol-induced relaxations in tracheal smooth muscle from estrus rats.