ABSTRACT
The emotional or affective component of pain regulates mood; it occurs primarily in the brain's limbic system; and a negative impact on affect is required in order for stimulus to be accurately portrayed as “painful.” The integration of sensory and affective components of pain and the ensuing activation of higher brain centers involved in the perception of noxious stimuli is an emerging topic within the field of pain neurobiology. A relationship between pain and mood has been supported by numerous clinical studies indicating significant comorbidity of chronic pain and various types of depressive illnesses. Besides the assumption that pain is simply a form of stress, the physiological basis for the coexistence of pain and depression is still being investigated. Studies described in this review address some of the cellular and molecular events occurring within the hippocampus that may be common to both pain and stress, possibly reflecting underlying mechanisms of chronic pain-related depression.