Common animal models for spasticity and pain

Animal models of spasticity and pain have allowed for the elucidation of possible mechanisms and the evaluation of potential therapeutic interventions for these serious clinical problems. Each model mirrors the clinical appearance of many features of the syndrome, but few reproduce the myriad patient reports of either intensity or relevant contributing factors, especially in models of chronic neuropathic pain. Often these models have been used to predict the potency and efficacy of pharmacologic agents that work in human pain states. Pain models have relied on measurements of the shifts in behavioral hypersensitivity to tactile and thermal stimuli, tests that are not used quantitatively in human patients. Even with the multiple peripheral and central models of spasticity and pain used in animals, only a few actually test human conditions: namely, diabetic neuropathy, chemotherapy, and immunotherapy for tumors. However, all these models have allowed for the comparison of certain behavioral, cellular, biochemical, and molecular mechanisms with human patient populations. Here we review the few extant models of spasticity, nerve injury, and central injury models of pain, and describe their features and use.