New Pain Mechanisms Revealed

Neuropathic pain is a chronic pain condition caused by a damaged or dysfunctional nervous system. It is characterised by shooting and burning pain that lasts long after the initial onset. Common causes of neuropathic pain include:

• alcoholism
• amputation
• back, leg and hip problems
• chemotherapy
• diabetes
• facial nerve problems
• HIV or AIDS
• multiple sclerosis
• shingles
• spine surgery

Unfortunately neuropathic pain doesn’t respond much to conventional analgesics but instead, antidepressants (amitriptyline and duloxetine) and anticonvulsants (gabapentin and pregabalin) have been found to help relieve pain.

A new study published in this month’s edition of Neuron by Thomas Nevian et al from the Department of Physiology at the University of Bern has revealed some of the mechanisms involved in neuropathic pain. In a mouse model, they found that neurons in the gyrus cinguli, a part of the brain found in the limbic system (usually associated with emotion) are modified by pain forming a “pain memory”. Neurons in the gyrus cinguli become more excitable due to a down-regulated ion channel. This leads to an increased number of nerve impulses which the brain perceives as pain.

The researchers managed to restore the function of the ion channel by activating a receptor sensitive to serotonin. This explains the success of some antidepressants in treating neuropathic pain. Nevian et al were able to identify the specific subtype of serotonin receptor that was more efficient at reducing the perception of pain. Excitingly, this could lead to the development of more effective drugs to treat neuropathic pain.