Riluzole interacts with voltage-activated sodium and potassium currents in cultured rat cortical neurons

doi:10.1016/S0306-4522(97)00604-0

Neuroscience

Volume 85, Issue 3, 24 April 1998, Pages 931-938

https://doi.org/10.1016/S0306-4522(97)00604-0 Get rights and content

Abstract

The actions of the neuroprotective and anticonvulsant agent riluzole on voltage-activated currents were studied in primary cultures of rat cortical neurons by using whole-cell patch-clamp recording techniques. Isolated Na⁺, Ca²⁺ and K⁺ currents were generated in these cells by depolarizing commands from a holding potential of −80 mV. Riluzole (10–300 μM) reversibly reduced in a dose-dependent manner the inward Na⁺ currents with an IC₅₀ of 51 μM in all the tested neurons (n=29). This drug also shifted the steady-state inactivation curve of the sodium current towards more negative values (about 20 mV, n=15) while it did not change significantly the decay phase of the Na⁺ current. Furthermore, riluzole (100 and 300 μM; n=5 and n=3, respectively) did not modulate the inward Ca²⁺ currents evoked by depolarizing steps on cortical cells. An additional concentration-dependent effect of riluzole was observed on the outward potassium currents. In fact, while the amplitude of the peak of the outward current (I_A) was not changed significantly, the amplitude of the late component of the outward K⁺ current (Iss) was markedly decreased during the perfusion of riluzole (IC₅₀=88 μM; n=16).

It is concluded that riluzole modulates the Na⁺- and the late K⁺-dependent currents in cortical neurons. Both phenomena may explain, at least in part, the anticonvulsant and neuroprotective properties of this compound.

Section snippets

Cell culture

Experiments were performed on neocortical neurons removed from 14 day Wistar rat embryos (Morini, Reggio Emilia, Italy) and grown in dissociated cell culture as described previously.6, 7Briefly, the animals were killed by decapitation under ether anaesthesia. Experiments were performed at 21–23°C, on neocortical neurons cultured for 12–16 days in Eagle's minimum essential medium (Gibco) with 5% rat serum, 6 mM of glucose, 2 mM of glutamine, and 100 μg/ml of gentamicine (Gibco). For more details,

Voltage-activated Na⁺ currents

In a first series of experiments, Ca²⁺ and K⁺ currents were pharmacologically blocked by extracellular application of Cd²⁺ and 4-AP as well as by the addition of Cs⁺ and TEA in the recording electrode. Under this experimental condition, depolarizing voltage commands from a holding potential of −80 mV elicited a voltage-dependent inward current (Fig. 1A) sensitive to TTX (complete block with 0.5 μM; data not illustrated). This inward Na⁺ current was maximally activated by a test pulse at −20 mV and

Discussion

Our findings have shown that riluzole induces multiple effects on voltage-activated currents in cultured rat cortical neurons. In fact. this drug causes: (i) a reversible and dose-dependent decrease of the Na⁺ current; (ii) a negative shift of the steady-state inactivation curve for the Na⁺ currents; (iii) a reversible and concentration-dependent reduction of the late K⁺ current. It is also worth mentioning that riluzole does not affect the fast transient outward currents, the voltage-dependent

Conclusions

The reduction of the Na⁺ current in cortical neurons and the shift of the steady-state inactivation Na⁺ curve might be related to the clinical effectiveness of riluzole as neuroprotectant. In fact, a depression of the voltage-activated Na⁺ current certainly reduces an excessive increase in cellular excitability and an enhanced release of excitatory amino acids.[23]These mechanisms might contribute to spare energy consumption and to preserve the ionic milieu during conditions of altered neuronal

Acknowledgements

The authors thank R. Sorge for the help in the statistical analysis and G. Gattoni and M. Federici for their excellent technical assistance.

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Riluzole interacts with voltage-activated sodium and potassium currents in cultured rat cortical neurons

Abstract

Section snippets

Cell culture

Voltage-activated Na+ currents

Discussion

Conclusions

Acknowledgements

Neuropharmacology

Neurosci. Lett.

J. Pharmac.

Brain Res.

Brain Res.

Neurosci. Lett.

Neurosci. Lett.

Eur. J. Pharmac.

Eur. J. Pharmac.

Trends pharmac. Sci.

Neuroscience

Neurosci. Lett.

Riluzole specifically blocks inactivated Na channels in myelinated nerve fibre

Eur. J. Physiol.

A controlled trial of riluzole in amyotrophic lateral sclerosis. ALS/Riluzole Study Group

N. Engl. J. Med.

Voltage-activated Na⁺ currents