Inhibitory Effect of Lomerizine, a Diphenylpiperazine Ca2+ -Channel Blocker, on Ba2+ Current Through Voltage-Gated Ca2+ Channels in PC 12 Cells
Inhibitory Effect of Lomerizine, a Diphenylpiperazine Ca2+ -Channel Blocker, on Ba2+ Current through Voltage-Gated Ca2+ Channels in PC 12 Cells Tomokazu Watanol, Hideaki Hara2,* and Takayuki Sukamoto2 1 Department of Pharmacology, New Drug Discovery Research Laboratory, Kanebo Ltd., 1-5-90 Tomobuchi-cho,of Pharmacology, Miyakojima-ku, New Drug Osaka R & 534,D Laboratory, Japan2Department Kanebo Ltd., 1-5-90 Tomobuchi-cho, Miyakojima-ku, Osaka 534, Japan Received July 8, 1997 Accepted August 22, 1997 ABSTRACT-We investigated the effect of lomerizine, an anti-migraine drug, on the Ba2+ current through voltage-gated Ca2+ channels in rat pheochromocytoma (PC12) cells using a whole-cell voltage-clamp tech nique. Lomerizine inhibited the Ba2+ current with an IC50 value of 1.9 ƒÊM. Lomerizine and nicardipine were > 4 times more potent than flunarizine, diltiazem, verapamil and dimetotiazine. The time course of inactivation induced by lomerizine was similar to that induced by nicardipine and flunarizine. These data indicate that lomerizine may inhibit the Ca2+ channel in a similar manner to nicardipine and flunarizine, and its potency is almost equal to that of nicardipine. Keywords: Lomerizine , Voltage-gated Ca2+ channel, PCl2 cell Calcium channel blockers are mainly divided into three Bio Medical, Kyoto) containing 7° fetal bovine serum types, namely, 1,4-dihydropyridine, phenylalkylamine (Moregate, Melbourne, Australia), 7% heat-inactivated and benzothiazepine types, from their structure (1). horse serum (Gibco, Grand Island, NY, USA), 2 MM L Lomerizine, 1-[bis(4-fluorophenyl)methyl]-4-(2,3,4 glutamine (Wako, Osaka) and 50 pg/ml gentamicin sul trimethoxybenzyl)piperazine dihydrochloride has been fate (Wako) at 37C in an atmosphere of 5% CO2.
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