PT  - JOURNAL ARTICLE
AU  - M Ichinose
AU  - P J Barnes
TI  - A potassium channel activator modulates both excitatory noncholinergic and cholinergic neurotransmission in guinea pig airways.
DP  - 1990 Mar 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1207--1212
VI  - 252
IP  - 3
4099  - http://jpet.aspetjournals.org/content/252/3/1207.short
4100  - http://jpet.aspetjournals.org/content/252/3/1207.full
SO  - J Pharmacol Exp Ther1990 Mar 01; 252
AB  - The effect of a potassium channel activator, cromakalim (BRL 34915), on excitatory nonadrenergic noncholinergic (e-NANC) and cholinergic neural bronchoconstriction was studied in guinea pigs. We monitored airway opening pressure as an index of airway caliber. After atropine (1 mg/kg iv.) and propranolol (1 mg/kg iv.), bilateral vagal stimulation evoked an e-NANC response. Cromakalim did not alter basal airway caliber, but reduced the e-NANC response to vagal stimulation in a dose-dependent manner, with a maximal inhibition of 71.9 +/- 9.2% (mean +/- S.E.) at 400 micrograms/kg i.v. (P less than .01). Pretreatment with phentolamine (2.5 mg/kg i.v.) had no effect on the inhibitory response produced by cromakalim but glibenclamide (25 mg/kg iv.), an inhibitor of ATP-sensitive potassium channels, blocked its effect. Cromakalim had no inhibitory effect on exogenous substance P (5-25 micrograms/kg i.v.)-induced bronchoconstriction. In animals depleted of tachykinins by capsaicin (50 mg/kg s.c.) pretreatment, cromakalim had an inhibitory effect on both vagalcholinergic and exogenous acetylcholine (0.3-2 micrograms/kg i.v.)-induced bronchoconstriction, although the inhibitory effect was significantly greater on neural stimulation. We conclude that potassium channels modulate both e-NANC and cholinergic neurotransmission, and to a lesser extent acetylcholine-induced bronchoconstriction in guinea pig airways.