VIP and PACAP: very important in pain?

Neuropathic pain arising from direct trauma to, or compression injury of, p eripheral nerves is a common clinical problem. It is characterized by the d evelopment of abnormal pain states (spontaneous pain, hyperalgesia, allodyn ia), which can persist long after the initial injury has resolved. The unde rlying mechanisms are poorly understood and, as a consequence, treatment is often unsatisfactory. Some of the main contributing factors are thought to be the morphological and phenotypic changes that occur centrally, includin g alterations in the expression of neurotransmitters and their associated r eceptors, both in the dorsal root ganglia and in the spinal dorsal horn. Th is article focuses on the functional role of the two structurally related p eptides VIP and PACAP within the spinal cord, and their possible contributi on to the altered transmission of sensory information in neuropathic condit ions.