Key result
NS-004 evoked concentration-related relaxations in guinea-pig tracheal smooth muscle, which were displaced by charybdotoxin or iberiotoxin.
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NS-004 induces relaxation in guinea-pig tracheal smooth muscle via activation of large conductance Ca(2+)-dependent K+ channels (BKCa).
The smooth muscle relaxant responses to NS-004, an activator of charybdotoxin-sensitive, large conductance Ca(2+)-dependent K+ channels (BKCa) were studied on the basal spontaneous tone in guinea-pig trachea in vitro. The sensitivity of these responses to a range of K+ channel inhibitors and antagonists were also evaluated. NS-004 (0.1-30 microM) evoked concentration-related relaxations (pIC50 5.48 +/- 0.13) on the spontaneous tone in guinea-pig tracheal rings, suspended in Krebs bicarbonate solution, with a maximum response not different to that to aminophylline (1 microM). Charybdotoxin (0.03 and 0.1 microM) or iberiotoxin (0.1 microM) significantly displaced the NS-004 concentration-response curve to the right of control with no change in maximum response. In contrast, glibenclamide (1.0 microM) apamin (0.1 microM) and dofetilide (1.0 microM) each failed to modify the responses to NS-004 on spontaneous tone in guinea-pig trachea. These results suggest that relaxations in guinea-pig tracheal smooth muscle to the substituted benzimidazolone, NS-004, involve the activation of BKCa channels.
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Lawson et al. (1997) studied this question. NS-004 vs. Control / K+ channel inhibitors was evaluated on Smooth muscle relaxant responses. NS-004 evoked concentration-related relaxations in guinea-pig tracheal smooth muscle, which were displaced by charybdotoxin or iberiotoxin.
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