Differential effects of riluzole on subpopulations of adult rat dorsal root ganglion neurons in vitro

Riluzole is clinically approved for the treatment of motoneuron disease. We have previously shown that this drug is neuroprotective for both sensory neurons and motoneurons and promotes neurite outgrowth [Bergerot A, Shortland PJ, Anand P, Hunt SP, Carlstedt T (2004) Exp Neurol 187(2):359-366; Shortland PJ, Leinster VH, White W, Robson LG (2006) Eur J Neurosci 24:3343-3353]. This study explored the effects of exogenous administration of 0.1 μM riluzole on the neurite growth of specific subpopulations of adult rat dorsal root ganglion (DRG) neurons in vitro. Neuronal branching and neurite length were measured in calcitonin gene related peptide (CGRP), Griffonia simplicifolia Isolectin B4 (IB4), N52 and parvalbumin positive neuronal subpopulations. Riluzole was found to enhance neurite branching in both CGRP and IB4 positive neurons compared to vehicle treated cultures. However, neurite length was only significantly increased in CGRP positive neurons in riluzole treated cultures. The results suggest that riluzole affects specific subpopulations of sensory neurons in vitro and that its effects may be mediated through activation of neurotrophic factor receptors, since neurite outgrowth could be blocked by the administration of K252a (at 10 nM). Riluzole may offer a new pharmacological approach to promote sensory regeneration following small fibre neuropathies.