M. Starec et al., INFLUENCE OF DYNORPHIN-A-(1-13) AND DYNORPHIN-A-(1-10) AMIDE ON STRESS-INDUCED ANALGESIA, Physiologia bohemoslovaca, 45(6), 1996, pp. 433-438
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.