"Pain" is a common phenomenon which has been experienced by most of us at some point of time. It is known that different defined physical stimuli like low pH and/or noxious heat, and different noxious substances activating different receptors at the peripheral nervous system induce pain. Apart from these defined stimuli, immune system of individual and his/her psychological state can also influence the pain to a large extent. However, in most of these cases, the pain is "acute" in nature. This kind of pain is transient and is directly related to the availability of the stimuli. In other words, in absence of these noxious stimuli, the acute pain decays fast if not vanishes.

However, in case of "chronic pain", the pain can be long lasting and medical treatment is not satisfactory. Also many analgesic drugs, like morphine which are effective against acute pain, are not effective against chronic pain. In fact, at present chronic pain has very little scope of medical treatment if at all. The factors involved in the development of chronic pain, their effect as well as their regulation remain unclear. In a simplified manner, the chronic pain can be partially explained by the permanent changes in the signaling events within the peripheral nervous system and by an alternate neuronal connections resulting abnormal transmission of the pain signal. At the neuronal level, changes in the cellular structures like mitochondria, cytoskeleton, vesicles and others may form the basis of chronification. Transient Receptor Potential (TRP) ion channels are also known to play central role in different forms of pain. Therefore, with regard to pain chronification, the involvement of TRP ion channels and other proteins involved in the regulation of different cellular components are worth to study at the molecular level.