Title: Effects of neostigmine on bronchoconstriction with continuous electrical stimulation in rats

Purpose. When neostigmine is used to reverse muscle relaxants in patients with asthma without signs of airway inflammation, asthma attack is encountered occasionally. It is likely that abnormally-increased electrical impulses traveling from brain through cholinergic nerves to airway smooth muscles may be one of the pathogeneses of asthma attack. We applied continuous electrical field stimulation (c-EFS) or continuous electrical stimulation (c-ES) with low frequency to vagal nerve of the rat in vitro and in vivo to determine the role of cholinergic nerve activation in inducing airway constriction. Methods. Fifty-seven male Wistar rats were used. In in vitro study we examined whether tetrodotoxin (TTX), a Na channel blocker, 4-DAMP, a muscarinic M3 receptor antagonist, or neostigmine could affect c-EFS-induced contraction of the tracheal ring. In in vivo study, we examined whether c-ES of vagal nerve could increase maximum airway pressure (Pmax), and neostigmine could potentiate c-ES-induced Pmax. Results. TTX and 4-DAMP completely inhibited c-EFS-induced contraction, while neostigmine potentiated c-EFS-induced contraction dose-dependently. Pmax was not increased by neostigmine. Pmax was not increased by 2-Hz c-ES, but increased by the addition of