INFLUENCE OF DYNORPHIN-A-(1-13) AND DYNORPHIN-A-(1-10) AMIDE ON STRESS-INDUCED ANALGESIA

Dynorphin A (1-13) and its analog dynorphin A (1-10) amide were applie d intracerebroventricularly in male ICR mice. Both dynorphins did not reveal any analgesic activity in tail-flick test under normal (non-str essed) conditions. However, in combination with stress (forced swimmin g or whole body vibration) both dynorphins prolonged tail-flick latenc ies when compared with stressed saline controls. Naloxone inhibited th e effect of dynorphins in forced swimming test. Neither dynorphin A (1 -13) nor dynorphin A (1-10) amide increased tail-flick latencies when combined with weak immobilization stress. Our results suggest that the analgesic effects of dynorphins are potentiated by strong stressors.