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 abuse disorders (SUD). Operant conditioning is the most widely used rodent model of SUD. However, most operant chambers do not accommodate more than one rat at a time. Here, we introduce PeerPub – a novel social operant chamber. PeerPub uses a touch sensor to record the number of licks on drinking spouts. It then delivers a drop of solution with a fixed volume as the reward to the tip of the spout when the number of licks meets the requirement of a reinforcement schedule. A radio-frequency identification (RFID) chip implanted on top of each rat’s skull tracks the identity of the rat. The system is controlled by a Raspberry Pi computer. We tested PeerPub using male Wistar Kyoto rats in daily one-hour sessions where supersac, a solution containing glucose and saccharin, was delivered under a fixed ratio 5 schedule. We found that male rats consumed more supersac in group housing rather than in isolated conditions. These data demonstrated the utility of PeerPub in modeling the interaction between motivated behavior and social context. We anticipate devices like PeerPub will help demonstrate the role of the social environment in SUD phenotypes. The design of PeerPub is available at http://github.com/nijie321/PeerPub