Evaluating the impact of age and inflammatory duration on behavioral assessments of nociception

Pain is a prevalent issue for elderly individuals. Unfortunately, it remains unclear how acute and chronic pain differs as a function of age, and surprisingly, there is even disagreement on how the sensory and affective dimensions of pain change with age. Therefore, the current investigation evaluated such age differences with behavioral methodology using a preclinical model of arthritis. The primary factors of interest were age and chronicity of pain using behavioral assessments designed to measure sensory and affective dimensions of pain processing. Mechanical and thermal paw withdrawal thresholds demonstrated unique outcomes associated with sensory processing across age. The processing of pain affect measured by the Place Escape/Avoidance Paradigm (PEAP testing) also demonstrated age related effects. Overall, younger animals appeared more sensitive to nociceptive stimuli than older animals. However, the results from the current study suggest that chronicity of pain can be impactful for how older animals process pain related affect and avoidance. The finding of unique patterns of pain across age and duration of pain highlights the clinical literature. Future research should aim to elucidate mechanisms for affective processing of chronic pain in older subjects.