A simple method for studying operant wheel running in rats.

A simple method for studying operant wheel running in rats. The present report describes an operant running device for rats. The apparatus makes use of an activity wheel driven by a small electric motor. The motor is started by a bar press; once activated, the wheel turns for 3-30 sec. depending on the setting of a timing device. The system is well suited to long term studies of activity patterns. Activity patterns Operant running Wheel running HORMONES, neurohumors and environmental manipulations all modify the level of spontaneous activity in rats. A complete understanding of the nature of these changes, however, requires more than a study of revolutions/time. It should also include the temporal duration and patterning of individual bouts of running. The present paper describes an apparatus that allows one to obtain these data. A standard 35.6 cm Wahmann activity wheel was modified by the addition of two heavy gauge sheet metal barriers shaped to conform to the wheel and mounted on the side wall by means of L-shaped flanges (Fig. 1). The purpose of these barriers is to limit exploration, thereby increasing the likelihood of bar pressing. One barrier holds a Lafayette bar press switch rewired to be normally closed; the upper portion of the barrier is angled toward the axle to prevent perching on the switch. The barrier's position represents a compromise between placing the bar parallel to the ground (maximizing the gravitational preload on the switch) and placing the bar in line with the running surface (maximizing accessibility for the animal). The other barrier, positioned above the axle, keeps the animal from climbing onto the axle but allows greatest running space. The revolution counter was disconnected from the axle and replaced by a V-belt pulley. A steel sleeve, I.D. = 0.79 cm, O.D. = 1.27 cm, centers the pulley on the axle. The drive pulley was connected to the wheel pulley by a V-belt which was notched to increase flexibility (see Fig. 1). Selection of a motor is governed by two criteria: (1) The motor must be of relatively low r.p.m, due to gearing limitations imposed by commercially available pulley combinations, and (2) the motor should sufficiently resist the tendency of the wheel to turn during the rat's explorations. A 100 V a.c. gear motor (Dayton 3M097) with an output of 50 r.p.m, geared down 2:1 to achieve a wheel speed of 25 r.p.m, was used. Figure …