Intrathecal dynorphin A (1-13) and (3-13) reduce spinal cord blood flow by non-opioid mechanisms.

: Dynorphin A (Dyn A)-related peptides have been implicated in the pathophysiology of spinal cord injury in part because their intrathecal (i.t.) injection causes hindlimb paralysis. The effects of paralytic doses of i.t. Dyn A (1-13) and Dyn A (3-13) on spinal cord blood flow and cardiac output were examined in rats using radiolabeled microspheres. Both Dyn A (1-13) and Dyn A (3-13) significantly reduced blood flow in lumbosacral spinal cord without altering cardiac output. Pretreatment with naloxone failed to block these reductions in blood flow. Thus, the paralytic effects of Dyn A may result from non-opioid actions of Dyn A to reduce spinal cord perfusion.