Training Rats Using Water Rewards Without Water Restriction.

Pamela Reinagel

doi:10.3389/fnbeh.2018.00084

Abstract

High-throughput behavioral training of rodents has been a transformative development for systems neuroscience. Water or food restriction is typically required to motivate task engagement. We hypothesized a gap between physiological water need and hedonic water satiety that could be leveraged to train rats for water rewards without water restriction. We show that when Citric Acid (CA) is added to water, female rats drink less, yet consume enough to maintain long term health. With 24 h/day access to a visual task with water rewards, rats with ad lib CA water performed 84% ± 18% as many trials as in the same task under water restriction. In 2-h daily sessions, rats with ad lib CA water performed 68% ± 13% as many trials as under water restriction. Using reward sizes <25 μl, rats with ad lib CA performed 804 ± 285 trials/day in live-in sessions or 364 ± 82 trials/day in limited duration daily sessions. The safety of CA water amendment was previously shown for male rats, and the gap between water need and satiety was similar to what we observed in females. Therefore, it is likely that this method will generalize to male rats, though this remains to be shown. We conclude that at least in some contexts rats can be trained using water rewards without water restriction, benefitting both animal welfare and scientific productivity.

Highlights

Operant conditioning tasks with food or water rewards are commonly used to train and test rodents in a wide variety of sensory, motor and cognitive tasks
We have shown that providing ad lib citric acid (CA) water can obviate the need for water restriction for behavioral tasks that depend on water rewards
In the context of a 24 h/day training protocol, the reduction in trial rate is minimal, while eliminating water restriction can dramatically reduce the amount of intervention required and increase the throughput of rodent training

Summary

Introduction

Operant conditioning tasks with food or water rewards are commonly used to train and test rodents in a wide variety of sensory, motor and cognitive tasks. Water rewards can be dispensed with temporal and quantitative precision and consumed rapidly with minimal body movement, which makes them ideal for automated behavioral training and testing and electrophysiological or optical recording. Live-in automated training systems eliminate the need for daily human intervention for training purposes. Water restriction requires a high level of monitoring, documentation and intervention by research staff, above and beyond the scope of routine animal husbandry. If it were possible to train rodents without water or food restriction, Training Rats Without Water Restriction behavioral training or testing in live-in systems could be provided in the context of routine daily health monitoring by animal husbandry staff, which could increase experimental throughput. Rodents will do trials for nutritive rewards (sugar water, juice, soy milk, peanut oil, etc.) without food or water restriction, but caloric rewards require more cleaning and maintenance of equipment and increase the risk of diabetes or obesity in the animals

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