[Modulation of cholinergic neurotransmission by Ca(2+)-activated K channel and Na(+)-K(+)-ATPase in canine airway smooth muscle].
Stimulation of Ca(2+)-activated K+ channel and Na(+)-K(+)-ATPase may play an important role in the relaxant responses of airway smooth muscle to certain bronchodilators. To elucidate whether cholinergic neuroeffector transmission can be modulated by Ca(2+)-activated K+ channel and Na(+)-K(+)-ATPase, we studied canine airway smooth muscle under isometric conditions in vitro. Addition of charybdotoxin (ChTx, 10(-7) M) did not alter the contractile responses to acetylcholine (ACh) but augmented electrical field stimulation (FES)-induced contractions at 1-10 Hz (p < 0.01), whereas apamin and glibenclamide were without effect. This effect was dose-dependent, with the maximal increase being 36.8 +/- 5.3% (p < 0.001). Ouabain at a concentration insufficient to alter the resting tension (10(-7) M) increased contractions induced by both EFS and ACh. The magnitude of the increase in contractile responses to EFS was similar to those to ACh at ouabain concentration of up to 3 x 10(-7) M, but the former was significantly greater at 10(-6) M ouabain (p < 0.05). These results suggest that each Ca(2+)-activated K+ channel and Na(+)-K(+)-ATPase may a modulatory role in the cholinergic neurotransmission by inhibiting the exocytotic ACh release from the vagal nerve terminals.
Tagaya
E
E
First Department of Medicine, Tokyo Women's Medical College.
Tamaoki
J
J
Isono
K
K
Takeyama
K
K
Chiyotani
A
A
Konno
K
K
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D001980:Bronchi / Q000187:drug effects; D004285:Dogs; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*; D014630:Vagus Nerve / Q000378:metabolism
D015221:Potassium Channels; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D000109:Acetylcholine