Intrathecal dynorphin A1-13 and dynorphin A3-13 reduce rat spinal cord blood flow by non-opioid mechanisms

Abstract Radiolabeled microspheres were used to examine the effects of paralytic intrathecal doses of dynorphin A (Dyn A 1–13 ) and Dyn A 3–13 on rat brain and spinal cord blood flows and cardiac output. Dyn A 1–13 produced significant dose-related reductions in blood flow to lumbosacral and thoracic spinal cord without altering cardiac output and blood flow to brain and cervical spinal cord. Naloxone failed to block these effects. Dyn A 3–13 , which lacks opioid activity, also significantly reduced blood flow in lumbosacral spinal cord. Thus, the paralytic effects of Dyn A in the rat may involve reductions in spinal cord resulting from non-opioid actions of Dyn A.