Lamotrigine increases intracellular Ca2+ levels and Ca2+/calmodulin-dependent kinase II activation in mouse dorsal root ganglion neurones.

Aim Lamotrigine is a neuroprotective agent that is used clinically for the treatment of seizures and neuropathic pain. A significant volume of literature has reported that lamotrigine exerts analgesic effect by blocking Ca²⁺ channels. However, little is known regarding the effect of lamotrigine on the intracellular Ca²⁺ concentration ([Ca²⁺]_i). The aim of this study was to determine whether lamotrigine modulates [Ca²⁺]_i in sensory neurones. Methods Lamotrigine-induced changes in [Ca²⁺]_i were measured in mouse dorsal root ganglion ( DRG) neurones using the Ca²⁺-sensitive fluorescent indicator Fluo 3- AM and a confocal laser scanning microscope. Ca²⁺/calmodulin-dependent kinase II (Ca MKII) activation was assessed by the fluorescence intensity using immunocytochemical procedures. Results Treatment with 1, 10, 30 or 100 μ m lamotrigine transiently increased [Ca²⁺]_i in DRG neurones in a dose-dependent manner. Treatment with 100 μ m lamotrigine induced a significant (threefold) increase in the Ca²⁺ peak in the presence or absence of extracellular Ca²⁺. The lamotrigine-induced Ca²⁺ increase was abolished or decreased by the treatment with a specific PLC inhibitor (U73122), IP3R antagonist (xestospongin C) or RyR antagonist (dantrolene). In some cells, treatment with 100 μ m lamotrigine caused a transient Ca²⁺ increase, and the Ca²⁺ levels quickly fell to below the basal Ca²⁺ level observed prior to lamotrigine application. The decrease in basal Ca²⁺ levels was blocked by the treatment with a Ca MKII inhibitor ( KN93). Immunocytochemical analysis indicated that lamotrigine treatment increased the expression of phosphorylated Ca MKII in DRG neurones. Conclusion Treatment with lamotrigine increased [Ca²⁺]_i apparently as a result of Ca²⁺ release from intracellular stores and Ca MKII activity. [ABSTRACT FROM AUTHOR]