Inhibitory Effects of Bifemelane on Brain Ca2+Channel Subtypes Expressed in Xenopus Oocytes.

Kinoshita Mariko, Kaneko Shuji, Yasuno Tohru, Yada Nobumichi, Akaike Akinori, Satoh Masamichi

doi:10.1254/jjp.78.39

Effects of the cerebroprotective agent bifemelane on voltage-dependent Ca²⁺ channel currents were evaluated in Xenopus oocytes expressing specific Ca²⁺-channel subtypes. Extracellular perfusion of bifemelane showed a dose-dependent blocking action on both N-type and Q-type Ca²⁺ channels, but not on cardiac L-type Ca²⁺ channels expressed in the oocytes, and the inhibitory action on Q-type current was stronger than that on N-type current. The time course of inhibition by bifemelane was comparatively slow; a 20-min perfusion with 1 μM bifemelane was required to reduce the amplitude of the Q-type current to 80% of the control level. When bifemelane was applied intracellularly, the potency and time-course of inhibition was equivalent to that caused by the perfusion of bifemelane. The bifemelane-induced inhibition was voltage-dependent but not use-dependent in Q-type channels since it was apparent at more depolarized potentials but not influenced by the interval of depolarization. These results suggest that bifemelane inhibits the opening of the specific Ca²⁺ channels located at nerve terminals to suppress excessive neurotransmitter release from neurons in some pathophysiological conditions such as ischemia.

Inhibitory Effects of Bifemelane on Brain Ca2+Channel Subtypes Expressed in Xenopus Oocytes.

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Inhibitory Effects of Bifemelane on Brain Ca2+Channel Subtypes Expressed in Xenopus Oocytes.

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