Double Decker Enrichment cages have no effect on long term nociception in neuropathic rats but increase exploration while decreasing anxiety-like behaviors

Abstract

In this present study, we investigated the impact of environmental enrichment in Sprague Dawley rats up to three months after a chronic or sham nerve injury. Sprague Dawley rats were housed in either standard polycarbonate cages or rat enrichment cages. Following 2 weeks of training and the recording of baseline behavioral values, half of the animals underwent a right sciatic nerve chronic constriction injury (CCI) surgery under general anaesthesia to induce chronic neuropathic pain. The other animals underwent a sham surgery. Animals were then evaluated once a month for 3 consecutive months in different behavioural tests for of mechanical and heat sensitivities as well as for exploration and anxiety-like behaviors. Mechanical and heat sensitivities were also tested at 15 days following the surgery. One month following the surgery, half of the rats in each group (CCI and sham) were either left in the standard rat cages or placed in the Double Decker cages. Environmental enrichment did not affect the mechanical or heat sensitivity of neuropathic animals; however exploration increased, and anxiety-like behaviours decreased, significantly (p<0.01). These results clearly show that environmental enrichment can have a significant impact on exploratory and anxiety-like behaviour in neuropathic rats without modifying pain hypersensitivity.