토끼 위 근위부의 비-아드레날린 비-콜린성 이완반응의 포타슘 체널에 의한 접합전 조절작용

Prejunctional Modulation of Non-adrenergic Non-cholinergic Relaxation of the Rabbit Proximal Stomach by Potassium Channels

The effects of different K+ channel blockers were investigated on the non-adrenergic non-cholinergic (NANC) relaxations in the circular muscle of the rabbit proximal stomach. Non-selective blockers of K+ channels, 4-aminopyridine (4-AP, 3~30mcM) and tetraethylammonium (TEA, 100~1000mcM) significantly enhanced the NANC relaxations in a concentration-dependent manner. The enhancement was more prominent for the NANC relaxations induced by the electric field stimulation (EFS) with lower frequencies. Blockers of large conductance Ca2+-activated K+ channels, charybdotoxin and iberiotoxin, a blocker of small conduntance Ca2+-activated K+ channels, apamin and a blocker of ATP-sensitive K+ channels, glibenclamide had no effect on the NANC relaxations, respectively. Exogeneous administration of nitric oxide (NO, 1~30mcM) caused concentration-dependent relaxations which showed a similarity to those obtained with EFS. None of the K+ channel blockers had an effect on the concentration-dependent relaxation in response to NO. These results suggest that prejunctional K+ channels regulate the release of NO from the NANC nerve in the rabbit proximal stomach as the inhibition of prejunctional K+ channels increases the NANC relaxation induced by the EFS.