Citalopram, a selective serotonin reuptake inhibitor augments harmaline-induced tremor in rats

Citalopram, a serotonin reuptake inhibitor (SSRI) is one of the widely used antidepressants. Apart from its antidepressant activity citalopram is also used for anxiety, panic disorders, obsessive-compulsive disorder and behavioral disturbances of dementia. Tremor is the second most common neurological adverse effect in patients receiving treatment with SSRIs. Use of these agents in depressed patients with essential tremor has not been studied. The present study was undertaken to investigate the effect of chronic citalopram treatment on harmaline-induced tremors in rats. Female Sprague-Dawley rats weighing 70+/-2 g were given citalopram in doses of 0, 10, 20 and 40 mg/kg by gavage for 2 weeks. On the 15th day, the rats were given harmaline (10 mg/kg, i.p.) 30 min after the last dose of citalopram. The latency of onset, intensity and duration of tremor and EMG were recorded. Serotonin (5HT) and 5-hydroxy indole acetic acid (5HIAA) were measured in brain stem. Citalopram dose dependently exacerbated the duration, intensity and amplitude of EMG of harmaline-induced tremor. A significant decrease in 5HT turnover (5HIAA/5HT ratio) in the brain stem was observed suggesting a possible role of serotoninergic impairment in citalopram-induced augmentation of harmaline-induced tremor. Clinical implications of these observations warrant further investigation.