Chronic pain is a persistent, complex condition that contributes to impaired mood, anxiety and emotional problems.
Osteoarthritis (OA) is one of the major causes of
chronic pain in adults and elderly people. A substantial body of evidence demonstrate that hippocampal neural circuits, especially monoamine
dopamine and
serotonin levels, contributes to negative affect and avoidance motivation experienced during
pain. Current pharmacological strategies for OA patients are unsatisfying and the
endocannabinoid system modulation might represent an alternative for the treatment of OA-related
pain. In the present study, we used a rat model of
osteoarthritis induced by
intra-articular injection of
sodium monoiodoacetate to assess, 28 days post-induction, the contribution of
endocannabinoid system on the possible alteration in pain perception and affective behavior, in LTP and monoamine levels in the lateral entorhinal cortex-dentate gyrus pathway. The results show that OA-related
chronic pain induces working memory impairment and depressive-like behavior appearance, diminishes LTP, decreases
dopamine levels and increases
serotonin levels in the rat dentate gyrus.
URB597 administration (i.p., 1 mg/kg) reduces
hyperalgesia and
mechanical allodynia, improves recognition memory and depressive-live behavior, restores LTP and normalizes monoamine levels in the hippocampus. The effect was observed 60-120 min post-treatment and was blocked by
AM251, which proves the action of
URB597 via the
CB1 receptor. Therefore, our study confirms the role of
anandamide in OA-related
chronic pain management at the behavioral and hippocampal levels. This article is part of the Special Issue on 'Advances in mechanisms and therapeutic targets relevant to
pain'.