Validation of a new computerized system for recording and analysing drug-induced tremor in rats.

INTRODUCTION Certain drugs can induce tremor in small animals and can be used as Parkinson's disease or essential experimental tremor models. However, the use of arbitrary scales for evaluating tremor in experimental models is limited by observer subjectivity. Progress in electronics and computer science has allowed a more precise quantification of tremor. The objective of the present study was to validate a newly developed low-cost method of spectral registration and analysis of tremor in free-moving rats. METHODS Male Wistar rats, 3-4 months of age, previously placed for 5 min inside a sensor cage, were administered with different doses of eserine (0.25-1.5 mg/kg), oxotremorine (0.25-1.5 mg/kg) or harmaline (7.5-60 mg/kg). Drug-induced tremor was recorded during 10 min using a computerized system composed of force transducers, a signal conditioning circuit, a digitizing interface and a microcomputer. The signal transmitted to the computer was quantified, stored and analyzed for its amplitude and frequency by means of specific programs. RESULTS Tremor was induced with an amplitude that was dose-dependent for all drugs used. Tremor frequency was dose-dependent for oxotremorine and eserine, but not for harmaline. The performance of the system was compared with that of other systems described in behavioral instrumentation literature. DISCUSSION The present data indicate that the new system is capable of detecting the tremor induced by drugs, and that the programs used for spectral analysis allow the quantification of the amplitude and the frequency of the tremor in free-moving rats.