• Hugo Leite-Almeida, Luis Almeida-Torres, Ana Raquel Mesquita, Antti Pertovaara, Nuno Sousa, João José Cerqueira, and Armando Almeida.
• Life and Health Sciences Research Institute, School of Health Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
• Pain. 2009 Jul 1; 144 (1-2): 57-65.

AbstractChronic pain syndromes encompass several clinical entities that frequently affect the individuals' emotional and cognitive behaviours which, in turn, can also alter pain perception. Additionally, both pain perception and motivational-affective behaviours change with increasing age. In order to evaluate the influence of age upon the interaction between chronic pain and affective/cognitive behaviours, 3-, 10- and 22-month-old rats with 1 month neuropathy (spared nerve injury, SNI model) were compared with age-matched sham-operated controls in the open field (OF; locomotor and exploratory behaviours), elevated plus-maze (EPM; anxiety-like behaviour), forced swimming (FST; depressive-like behaviour), working memory water maze (WM; spatial short-term memory), Morris water maze (MWM; spatial reference memory) and spatial reversal (behavioural flexibility) tests. Locomotor and exploratory activities decreased steadily with age and were further reduced by SNI. Aging was associated with increased anxiety-like behaviour, which was potentiated by SNI in both 3- and 22-month-old rats. The performance in the FST was affected by SNI but only in mid-aged animals. Cognitive performances in the MWM and spatial reversal tests deteriorated with age; however, the SNI lesion was only detrimental in the reversal task to mid-aged animals. Our data demonstrate that the influence of neuropathic pain on affective and cognitive behaviours is age dependent and varies with the behavioural domain that is tested. Importantly, mid-aged animals seem to be more susceptible to depression and cognitive deterioration associated to chronic pain than young and old groups.

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