Objective: To study the effect of pretreatment with low doses of vanillin, a flavoring agent used as a food additive, on harmaline-induced tremor in rats.
Methods: Sprague Dawley rats (110 ± 5 g) were divided into groups of six animals each. Vanillin (6.25 mg, 12.5 mg, and 25 mg/kg) was administered by gavage to different groups of rats, 30 minutes before the induction of tremor. Harmaline (10 mg/kg, i.p.) was used for the induction of tremor. The latency of onset, duration, tremor intensity, tremor index, and spontaneous locomotor activity were recorded. A separate batch of animals was used for the determination of serotonin (5HT) and 5 hydroxyindole acetic acid (5HIAA) levels in the brain.
Results: Harmaline treatment resulted in characteristic tremor that lasted for more than 2 hours and decreased the locomotor activity of rats. Pre-treatment with vanillin significantly reduced the duration, intensity, and tremor index of harmaline-treated animals. Vanillin treatment also significantly attenuated harmaline-induced decrease in the locomotor activity. An increase in 5HT levels and the changes in 5HIAA/5HT ratio observed in harmaline treated rats were significantly corrected in vanillin pretreated animals.
Discussion: Vanillin in low doses reduces harmaline-induced tremor in rats, probably through its modulating effect on serotonin levels in the brain. These findings suggest a beneficial effect of vanillin in essential tremor.
Keywords: Harmaline; serotonin; 5 hydroxyindole acetic acid; tremor; vanillin.