Dynorphin a peptides - Potential role in pain transmission and therapy

Dynorphin (DYN) is a potent endogenous opioid peptide which binds with high affinity to the kappa-opioid receptor and has lower affinity for other opi oid and non-opioid [N-methyl-D-aspartate (NMDA)] receptors. This pharmacolo gical profile may explain the conflicting results obtained with DYN in expe rimental pain models. Most recent literature suggests that DYN contributes to the spinal analgesic effects of cannabinoids. In neuropathic pain, DYN a nd its fragments seem to contribute to the allodynia via activation of spin al NMDA receptors. Interestingly, DYN attenuates opioid withdrawal and tole rance. The present data do not clearly identify a role for DYN in clinical pain therapy; however, a preliminary report suggests that it provides effec tive pain relief in patients with chronic cancer pain.