Intravenous anesthesia

Abstract

Anesthesia and Pain Medicine. 2004 Sept. 8(3): 172-179
ⓒ Korean Society for Intravenous Anesthesia
  
 
 
The Interaction of Intrathecally Coadministered Morphine and Adenosine A1 Receptor Antagonist (DPCPX) on Mechanical Allodynia in Rats with a Spinal Nerve Ligation
Jong Yeon Park, M.D., In Gu Jun, M.D., and Mi Young Kwon, M.D.
Department of Anesthesiology and Pain Medicine, College of Medicine, University of Ulsan, Seoul Asan Medical Center, Seoul, Korea
 

Background: Usually the antiallodynic effect of morphine is attenuated in a neuropathic rat model and a linkagebetween adenosine and opioid is insisted for the reason. However, in our previous study, spinal morphine was found to have an antiallodynic effect in a neuropathic rat model. The present study was performed to observe the interaction of morphine and adenosine A1 receptor antagonist (DPCPX) on mechanical allodynia in rats with a spinal nerve ligation.
Methods: Male rats were prepared by tightly ligating the left L5, 6 spinal nerves and by implanting a lumbar intrathecal catheter. First, morphine at 0.1, 1mug or saline was administered intrathecally to examine changes in the mechanical antiallodynic effect. Second, DPCPX 30, 100mug was co-administered with R-PIA 3, 10mug to confirm the reversal of the mechanical antiallodynic effect of R-PIA. Finally, DPCPX 30, 100mug was co-administered with morphine 0.1, 1mug to investigate the reversal of the mechanical antiallodynic effect. The mechanical allodynic thresholds to von Frey hairs were assessed and converted to %MPE.
Results: The allodynic threshold was significantly increased by morphine 0.1, 1mug. DPCPX 30, 100mug reversed the antiallodynic effect of R-PIA 3, 10mug. The intrathecally co-administered DPCPX 30, 100mug reversed the antiallodynic effect of morphine 0.1mug, but not 1mug.
Conclusions: It is suggested that the antiallodynic effect of morphine is partially related to adenosine A1 receptor and in a low dose morphine the role of adenosine A1 receptor is more important in a rat model of spinal nerve ligation.
 
Key words : Adenosine receptor, allodynia, DPCPX, morphine, μ-opioid receptor, R-PIA
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