The emotion of pain and its chemistry.

Pain is not an electrical impulse derived from tissue injury but an emotional experience arising when a nervous input is interpreted in the light of experience and emotional context as being 'painful'. Pain may thus signify tissue damage, vivid sensory experience or inner turmoil. Pain may be distressing but it can also be pleasurable. Whether a given stimulus provokes pain and whether that emotional feeling causes distress varies from individual to individual and from moment to moment. The brain possesses chemically mediated mechanisms that can exert control over the experience of 'pain'. An understanding of such mechanisms suggests new approaches to the relief of distressing pain (and to the artificial production of pleasurable pain).