A new method for quantification of tremors in mice.

A procedure for quantifying whole-body tremors in mice was developed. Displacement of a free-floating platform by animal movement created a change in resistance across a strain gauge. The resulting resistive changes were assessed as voltage fluctuations by a wheatstone bridge and converted into an intensity-frequency profile by a series of calculations involving Fourier transformations. Movement profiles of normal mice were characterized by high-intensity, low-frequency peaks. Administration of oxotremorine, 2.5 mg/kg, ip, produced numerous high-frequency, high-intensity peaks within 5 min of administration. The peak frequency at 5 min after oxotremorine was approximately 15 Hz, and within 30 min the intensity-frequency profile had returned to control levels. In dose-response studies, a slight decrease in exploratory activity and initiation of low-level tremors was observed after 0.5 mg/kg. The most severe tremors were detected after a dose of 1.0 mg/kg. The peak frequency remained at approximately 15 Hz at 1.0 to 5.0 mg/kg, but varied greatly in intensity. This study describes an inexpensive, quantitative, sensitive, and rapid technique for quantifying tremors in mice.