ABSTRACT
BACKGORUND: inhalation anesthetics have been known as bronchodilators, and there are reports that enflurane has some relaxing effects on tracheal smooth muscles. However, there are not so many reports on the ACh release in the postganglion nerve endings. We tried to evaluate the effect of enflurane on the contraction of the tracheal smooth muscle in the postganglion nerve ending in guinea pigs. METHODS:isolated tracheal preparations of guinea pigs were used and contractions were induced by electrical field stimulation (3 Hz & 30 Hz). in the pilocarpine- enflurane group, pilocarpine (10(-5) M) was administrated and enflurane (1 MAC and 2 MAC) was administered. in the gallamine-enflurane group, gallamine (10(-6) M) was administrated and enflurane (1 MAC and 2 MAC) was administered. in the enflurane 1 MAC group and 2 MAC group, contractions were induced by electrical field stimulation before and after administration of enflurane. The percentile contraction to the contraction induced by acetylcholine (10(-4) M) were evaluated. RESULTS: The potentiation of the contraction which was induced by electrical field stimulation was observed by enflurane administration and with prior administration of pilocarpine (10(-6) M), with prior administration of gallamine (10(-5) M). There was no potentiation of contractions, but potentiation of the contraction was observed with enflurazne (2 MAC, 30 Hz). CONCLUSiONS:Enflurane potentiates the contraction induced by electrical field stimulation in guinea pig tracheal smooth muscle. These findings seem to be related with prejunctional M2 receptor in the postganglionic nerve endings.