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ANESTHETIC PHARMACOLOGY

The Local Anesthetic Butamben Inhibits Total and L-Type Barium Currents in PC12 Cells

From the Department of Neurophysiology, Leiden University Medical Center (LUMC), Leiden, The Netherlands.

Address correspondence to Dirk L. Ypey, PhD, Department of Cardiology (C5-27), Leiden University Medical Center (LUMC), Postbox 9600, 2300 RC Leiden, The Netherlands. Address e-mail to D.L.Ypey{at}LUMC.NL.

BACKGROUND: Butamben or n-butyl-p-aminobenzoate is a long-acting experimental local anesthetic for the treatment of chronic pain when given as an epidural suspension. We have investigated whether Cav1.2/L-type calcium channels may be a target of this butamben action.

METHODS: The effect of butamben on these channels was studied in undifferentiated rat PC12-cells with the whole-cell patch-clamp technique in voltage-clamp. Ba²⁺ ions were used as the charge carriers in the calcium channel currents, whereas K⁺ currents were removed using K⁺ free solutions.

RESULTS: Butamben 500 µM reversibly suppressed the total whole-cell barium current by 90% ± 3% (n = 15), whereas 10 µM nifedipine suppressed this barium current by 75% ± 7% (n = 6). Preexposure to butamben followed by washout decreased the inhibition by nifidepine to 47% ± 5% (n = 10). These suppressive effects were not due to the measurement procedure and the drug vehicles in the solutions (<0.1% ethanol; n = 6).

CONCLUSIONS: Butamben inhibits the total barium current through expressed calcium channel types in PC12 cells, including Cav1.2/L-type channels. Because Cav1.2 channels may also occur in human nociceptive C fibers, this result allows the possibility that these L-type channels are involved in the analgesic action of butamben.