The plastic changes of peripheral and central nervous system have been examined extensively in animal models of chronic pain. A variety of neurotransmitters, neuromodulators, neurotrophic factors and their receptors exhibit dynamic changes in the chronic pain conditions, and the changes of these molecules are suggested to have important roles in the pathomechanisms of chronic pain.
In the chronic pain, a cancer pain is supposed to include almost all aspects of pain mechanisms. Three key categories, such as nociceptive pain, neuropathic pain and psychological pain, are most important when we consider the pathomechanisms of cancer pain. In this paper the two important molecular mechanisms of cancer pain, nociceptive pain and neuropathic pain are discussed.