Complexe amygdalien, douleurs et analgésie

The amygdaloid complex, or amygdala, is a structure of the temporal lobe thought to be involved in assigning emotional significance to environmental information. Pain having a strong affective and emotional dimension, the amygdala, especially its central nucleus (CeA), has emerged in the last 20 years as key element of the pain matrix. The CeA receives multiple nociceptive information from the brainstem, as well as highly processed polymodal information from the thalamus and the cerebral cortex. It also possesses the connections, which allow influencing most of the descending pain control systems as well as higher centers involved in emotional, affective and cognitive functions. Functional data collected using animal models indicate that the integration of nociceptive inputs in the CeA only marginally participates to sensory-discriminative components of pain, but rather contributes to associated behavior and affective responses. The CeA doesn't influence responses to acute nociception in basal condition, but induces hypoalgesia during aversive situation, such as stress or fear. On the contrary, during persistent pain states (inflammatory, visceral, neuropathic), a long-lasting functional plasticity of CeA activity contributes to an enhancement of the pain experience, including hyperalgesia, aversive behavioral reactions and affective anxiety-like states.