Effects of riluzole on harmaline induced tremor and ataxia in rats: biochemical, histological and behavioral studies.

Essential tremor (ET) is one of the most common and most disabling movement disorders among adults. The drug treatment of essential tremor remains unsatisfactory. Additional therapies are required for patients with inadequate response or intolerable side effects. Thus, we aimed to investigate the therapeutic effects of riluzole on harmaline-induced tremor and ataxia in rat, and determining whether riluzole exerts its effect through modulation of glutamate levels in cerebellum. The study included 5 groups of Wistar rats weighing 80-100g, injected with harmaline (50mg/kg i.p.) for inducing experimental tremors and ataxia. The rats in group 1 served as control (saline induced) and group 2 received harmaline alone, whereas the animals in groups 3, 4 and 5, were also given riluzole intraperitoneally at doses of 2, 4 and 8 mg/kg 10 min after harmaline administration, respectively. The intensity and duration of tremor were recorded. Rotarod test, distance traveled and number of crossings were used to evaluate motor performance. Results of this study demonstrated that riluzole dose dependently attenuated duration and intensity of harmaline-induced tremors. Also, riluzole significantly improves time to fall, distance traveled and number of crossings in combined riluzole and harmaline treated rats. Histological analysis indicated that harmaline could cause vermis Purkinje cell (PC) loss and riluzole prevented this toxic effect. Harmaline also could increase glutamate levels in vermis and treatment with riluzole restored glutamate levels. In conclusion, riluzole has relatively protective effects on harmaline-induced tremor, probably related to its inhibitory effect on glutamatergic neurotransmission.