Abstract
The insistent signal of pain is a warning to the body of a threatening event. Painful sensations in the limbs and internal organs signal illness or injury, causing us to rest and thereby give the body's defence system a chance to eliminate the source of harm. On the other hand, prolonged tissue damage or injury often leads to chronic pain states such that noxious stimuli evoke hyperalgesia and innocuous tactile stimuli evoke pain or pain-related behavior (allodynia). The underlying mechanisms for these pathological conditions involve plastic changes in synaptic transmission in the spinal cord.
