PAW, a cost-effective and open-source alternative to commercial rodent running wheels

Abstract

Voluntary wheel running is a common measure of general activity in many rodent models across neuroscience and physiology. However, current commercial wheel monitoring systems can be cost-prohibitive to many investigators, with many of these systems requiring investments of thousands of dollars. In recent years, several open-source alternatives have been developed, and while these tools are much more cost effective than commercial system, they often lack the flexibility to be applied to a wide variety of projects. Here, we have developed PAW, a 3D Printable Arduino-based Wheel logger. PAW is wireless, fully self-contained, easy to assemble, and all components necessary for its production can be obtained for only $75 CAD. Furthermore, with its compact internal electronics, the 3D printed casing can be easily modified to be used with a wide variety of running wheel designs for a wide variety of rodent species. Data recorded with the PAW system shows circadian patterns of activity which is expected from mice and is consistent with results found in the literature. Altogether, PAW is a flexible, low-cost system that can be beneficial to a broad range of researchers who study rodent models.

Keywords: Activity Monitoring; Exercise; Home Cage Recording; Running Wheel.

Graphical abstract

Fig. 1

Electronics assembly. A. Photograph showing the components required for assembling the PAW system. To assemble the required ground wire junctions, (B) wire segments are trimmed and stripped, (C) wrapped around one another, (D) and soldered then wrapped with heat-shrink tubing. To assemble the required power wire junctions, (E) wire segments are stripped, (F) wrapped around one another, (G) and soldered then wrapped with heat-shrink tubing. H. Schematic showing the wiring of the necessary PAW components. I. Photograph of the fully soldered PAW system. J. Photograph of the fully assembled electronic component.

Fig. 2

Full assembly of PAW. A. The Dome and Base components of the PAW system, 3D-printed with PLA. Four M3x12 screws were inserted into the base (B) which are then used to hold the electronics in place using the holes on the Arduino Microcontroller board (C). D. The Base is then secured to the Dome with three M3x8 screws. E. The Bio-Serv Mouse Igloo fits securely over the Dome. F. A strong magnet is glued to the inside of the Bio-Serv Fast-Trac wheel, (G) which is then mounted onto the Mouse Igloo. Fully assembled PAW systems in commonly used mouse laboratory home cages from (H) Ancare (N10 Mouse) and (I) Techniplast (GM500).

Fig. 3

Experimental validation of PAW. Wheel running activity was assessed using PAW. A. Mean hourly running distance recorded from across one week for cages of male (n = 6 cages; 5 mice per cage) and female (n = 6 cages, 5 mice per cage) mice. Lights were turned on at ZT0 and turned off at ZT12. B. Male and female mice recorded greater running activity during the dark phase, while lights were off, than during the light phase. C. The mean distance travelled per cage increased over the course of the week.