Proceedings of The Physiological Society

University of Cambridge (2008) Proc Physiol Soc 11, PC107

Poster Communications

Levetiracetam inhibits calcium signalling in cultured dorsal root ganglia neurons from neonatal rats

M. Ozcan1, E. Alcin2, S. Kutlu2, A. Ayar2

1. Biophysics, Firat University, Medical School, Elazig, Turkey. 2. Physiology, Firat University Faculty of Medicine, Elazig, Turkey.

Although the novel antiepileptic drug levetiracetam (LEV) have been shown to be effective in the treatment of pain, the mechanisms mediating its antinociceptive actions are still not well understood. The aim of this study was to investigate the effects of LEV on Ca2+ transients, evoked by high-K+ (30 mM) in cultured rat dorsal root ganglion (DRG) neurons. DRG neuronal cultures were loaded with 5 μmol Fura-2 AM and Ca2+ responses to stimulation with high-K+ were assessed by using the fluorescent ratiometry. Fura-2 loaded DRG cultures were excited at 340 and 380 nm, and emission was recorded at 510 nm by using imaging system consisting of CCD camera coupled to an inverted microscope with a 40x (1.30 NA S Fluor, Oil) objective. High-K+ responses were determined by the change in 340/380 ratio (basal-peak) and the area under the fluorescence ratio-time curve (AUC) was also calculated for individual DRG neurons in selected microscopic fields. All data were analyzed by using an unpaired t test, with a 2-tailed P level of <.05 defining statistical significance. LEV dose-dependently reduced the [Ca2+]i increase, elicited by 30 mM KCl, in a reversible manner. The mean 340/380 nm ratio was 1.18±0.06 (baseline, n=17), 1.15±0.06 (30 µM LEV, P>0.05, n=17) and 1.17±0.05 (recovery, n=17); 1.28±0.04 (baseline, n=17), 1.14±0.03 (100 µM LEV, P>0.05, n=17) and 1. 28±0.03 (recovery, n=17); 1.21±0.03 (baseline, n=18), 1.08±0.02 (300 µM LEV, P>0.05, n=18), and 1.21±0.02 (recovery, n=18), respectively. The AUC changes were consistent with the mean ratio results; the effects of 100 and 300 µM LEV being significant. Our results indicate that LEV significantly suppressed depolarisation-induced intracellular calcium changes in a dose-dependent fashion in dorsal root ganglion neurons. The inhibition of calcium signals in these sensory neurons by levetiracetam might contribute to the antinociceptive effects of the drug. Keywords: Levetiracetam; dorsal root ganglia, fluorescence calcium imaging, pain, sensory neurons

Where applicable, experiments conform with Society ethical requirements