Potent blockade of sodium channels and protection of brain tissue from ischemia by BⅢ 890 CL

摘要

We have synthesized a new benzomorphan derivative, 2R- [2α,3(s~*),6α]-1,2,3,4,5,6- hexahydro-6,11,11-trimethyl-3-[2-(phenyl- methoxy)propyl]-2,6-methano-3-benzazococin-10-ol hydrochloride (BⅢ 890 CL), which displaced [~3H]batrachotoxinin A-20α-benzoate from neurotoxin receptor site 2 of the Na~+ channel in rat brain synapto- somes (IC_50 = 49 nM), but exhibited only low affinity for 65 other receptors and ion channels. BⅢ 890 CL inhibited Na~+ channels in cells transfected with type IIA Na~+ channel α subunits and shifted steady- state inactivation curves to more negative potentials. The IC_50 value for the inactivated Na~+ channel was much lower (77 nM) than for Na~+ channels in the resting state (18 μM). Point mutations F1764A and Y1771A in transmembrane segment S6 in domain IV of the α subunit reduced the voltage- and frequency-dependent block, findings which suggest that BⅢ 890 CL binds to the local anesthetic receptor site in the pore. BⅢ 890 CL inhibited veratridine-induced glutamate release in brain slices, as well as glutamate release and neurotoxicity in cultured cortical neurons. BⅢ 890 CL (3-30 mg/kg s.c.) reduced lesion size in mice and rats when administered 5 min after permanent focal cerebral ischemia at doses that did not impair motor coordination. In contrast to many other agents. BⅢ 890 CL was neuroprotective in both cortical and subcortical regions of the rat brain. Our results demonstrate that BⅢ 890 CL is a potent, selective, and highly use- dependent Na~+ channel blocker that protects brain tissue from the deleterious effects of focal cerebral ischemia in rodents.