Measuring Behavior 2005: Blackburn-Munro

Pain-like behaviors in animals: How human are they?

G. Blackburn-Munro

Department of Pharmacology, NeuroSearch A/S, Ballerup, Denmark

The use of genetically-manipulated animals in conjunction with classical physiological and biochemical measurement have unravelled many of the pathological changes that occur in animal models of chronic pain, and these bear some striking similarities to those described in various human chronic pain conditions. In the following presentation, I will discuss several possible limitations in the validation of animal models of chronic pain, with emphasis placed on neuropathic pain models, and the methods used for assessing pain-like or nociceptive behaviors in these models. The majority of preclinical pain researchers invariably measure drug effects on evoked nociceptive behaviors such as hyperalgesia and allodynia, in response to thermal or mechanical stimulation of an injured hindpaw. In contrast, drug effects on spontaneous or evoked behaviors as typified by hindpaw flinching or hindlimb weight bearing are far less frequently reported. And yet, patients suffering from chronic pain, especially that which is neuropathic in origin frequently present with a diverse constellation of symptoms inclusive of spontaneous pain and hypersensitivity to stimulation. Chronic pain patients may also suffer from comorbid psychiatric illness as typified by depression. It is now well accepted that long term stress contributes to the pathophysiology of depression, an effect which is mediated by inappropriate hypothalamo-pituitary adrenal (HPA) stress axis function. Surprisingly, very little information exists pertaining to the effects of chronic pain (a known physical stressor) on HPA function in relevant preclinical animal pain models. Based on these and other observations, alternative methods for assessing pain and stress in animals, that may better reflect the diverse symptomotology of chronic pain in humans shall be proposed.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.