Harmaline-Induced Tremor in Mice: Videotape Documentation and Open Questions About the Model

BACKGROUND Harmaline-induced tremor in rodents has been extensively used as an animal model for essential tremor (ET). However, there is no visual documentation in the published literature. METHODS We injected mice subcutaneously with either 20 mg/kg of harmaline hydrochloride or saline and then videotaped the responses. RESULTS Action and postural tremor in the mouse began 5 minutes after subcutaneous harmaline injection and peaked at approximately 30 minutes. The tremor involved the head, trunk, tail, and four limbs and lasted for approximately 2 hours. The forelimb tremor was postural or action tremor, similar to that observed in ET. DISCUSSION This video segment provides the first visual documentation of the phenomenology of harmaline-induced tremor in a mouse. We also raise several unanswered questions regarding the use of harmaline-induced tremor to model ET.