The tolerometer: a fast, automated method for the measurement of righting reflex latency in chronic drug studies

We describe a fast, automated system for the measurement of righting reflex latencies in drug studies. This system, which we call a 'tolerometer', is especially useful for studies of drug tolerance which require a simple measurement of motor behaviour on a daily basis, for long periods of time. The tolerometer consists of a semi-cylindrical platform positioned on a 2 kg load cell, connected to a strain gauge amplifier (Radio Spares Ltd). The output from the amplifier is connected to a MacLab data acquisition system (Analog Digital Instruments), controlled by a Macintosh Classic computer. The MacLab Chart program is used to display, on the Macintosh screen, the load changes which occur during a righting reflex; sampling frequencies up to 40 kHz can be used, but we find 20-100 Hz adequate. Using measurement cursors provided by the Chart program, the latency from the point at which an animal is placed on the tolerometer platform in the supine position, until the completion of a righting reflex, can be measured accurately and easily.