Long term chronic pain, mainly inflammatory or neuropathic, afflicts about 25% of the general world population. More than 60% of people aged 65 plus complain of daily pains. This degree of disability has a huge economic toll in terms of loss of employment and disability payments but quality of life is equally compromised. Pain is thus a major medical issue but is not simply a sensation but an event that also triggers aversive and threatening psychological feelings. The importance of understanding the ways by which the central nervous system can alter incoming signals that relate to pain processing stimulated an increasing number of investigations many of which are concentrated on two first elements in the pain pathway – dorsal root ganglion (DRG) and dorsal horn (DH) neurons. Multiple and possibly common mechanisms appear to be involved in generation of chronic pain on the level of primary and secondary sensory neurones independently of aetiological diagnosis of pain. Molecular mechanisms leading to changes in patterns of action potential generation in primary neurones, modification of synaptic transmission between primary central afferents and secondary dorsal horn neurones and spinal neuron hyperexcitability acting in concert contribute to generation of chronic pain. In spite of profound difference in patterns of changes or damage in primary and secondary nociceptive neurones the pain syndromes as observed in numerous studies conducted on different animal models are generally common. Thus, there is a reason to believe that multiple and common mechanisms may be present in chronic pain conditions of all aetiologies.
Tutor of the course:
Dr. N. Voitenko, Bogomoletz Institute of Physiology, Kiev, Ukraine