PeerPub: A Device for Concurrent Operant Oral Self-Administration by Multiple Rats

The social environment has long been recognized to play an important role in substance use, which is often modeled in rodents using operant conditioning. However, most operant chambers only accommodate one rodent at a time. We present PeerPub-a unique social operant chamber. PeerPub employs touch sensors to track the licking behavior on drinking spouts. When the number of licks meets a set reinforcement schedule, it dispenses a drop of solution with a fixed volume as a reward at the tip of the spout. A radio frequency identification (RFID) chip implanted in each rat's skull identifies it throughout the experiment. The system is managed by a Raspberry Pi computer. We evaluated PeerPub using Sprague Dawley rats in daily 1 h sessions, where supersac (a glucose and saccharin solution) was provided under a fixed-ratio five schedule. We discovered that male rats consumed more supersac in dual rat conditions compared with single rat conditions. These findings illustrate PeerPub's effectiveness in modeling the interaction between motivated behavior and social context. We expect devices like PeerPub will help highlight the role of social environments in substance use disorder phenotypes. All computer code, 3D design, and build instructions for PeerPub can be found at http://github.com/nijie321/PeerPub.