TY - JOUR
T1 - Role of spinal NO in antiallodynic effect of intrathecal clonidine in neuropathic rats
AU - Pan, Hui Lin
AU - Chen, Shao Rui
AU - Eisenach, James C.
PY - 1998/12
Y1 - 1998/12
N2 - Background: The role of spinal nitric oxide (NO) in neuropathic pain remains uncertain. Although intrathecal clonidine causes NO release in the spinal cord, the functional role of spinal NO in clonidine-produced analgesia has not been examined. The objectives of this study were to assess the role of spinal NO in maintenance of allodynia and to determine the role of spinal NO in the antiallodynic effect of intrathecal clonidine. Methods: Allodynia was produced in rats by tight ligation of the left L5-L6 spinal nerves. Intrathecal catheters were inserted with tips in the lumbar intrathecal space. Mechanical allodynia was determined by application of von Frey filaments to the left hindpaw. In the first series of experiments allodynia was assessed before and after intrathecal injection of saline, L-arginine, an NO donor (SNAP), two NO synthase inhibitors (TRIM and NMMA), or an NO scavenger (PTIO). In the second series of experiments, 20 μg of clonidine was injected intrathecally 15 min after intrathecal injection of saline, TRIM, NMMA, or PTIO. Results: Allodynia was not affected significantly by intrathecal injection of L-arginine, SNAP, TRIM, NMMA, or PTIO. The antiallodynic effect produced by intrathecal injection of clonidine was attenuated significantly by pretreatment with TRIM, NMMA, or PTIO. Conclusions: These results demonstrate that spinal NO neither contributes significantly to maintenance of allodynia nor produces detectable antiallodynic effect in this neuropathic pain model. Furthermore, this study provides functional evidence that spinal NO plays an important role in the antiallodynic effect of intrathecal clonidine in neuropathic pain.
AB - Background: The role of spinal nitric oxide (NO) in neuropathic pain remains uncertain. Although intrathecal clonidine causes NO release in the spinal cord, the functional role of spinal NO in clonidine-produced analgesia has not been examined. The objectives of this study were to assess the role of spinal NO in maintenance of allodynia and to determine the role of spinal NO in the antiallodynic effect of intrathecal clonidine. Methods: Allodynia was produced in rats by tight ligation of the left L5-L6 spinal nerves. Intrathecal catheters were inserted with tips in the lumbar intrathecal space. Mechanical allodynia was determined by application of von Frey filaments to the left hindpaw. In the first series of experiments allodynia was assessed before and after intrathecal injection of saline, L-arginine, an NO donor (SNAP), two NO synthase inhibitors (TRIM and NMMA), or an NO scavenger (PTIO). In the second series of experiments, 20 μg of clonidine was injected intrathecally 15 min after intrathecal injection of saline, TRIM, NMMA, or PTIO. Results: Allodynia was not affected significantly by intrathecal injection of L-arginine, SNAP, TRIM, NMMA, or PTIO. The antiallodynic effect produced by intrathecal injection of clonidine was attenuated significantly by pretreatment with TRIM, NMMA, or PTIO. Conclusions: These results demonstrate that spinal NO neither contributes significantly to maintenance of allodynia nor produces detectable antiallodynic effect in this neuropathic pain model. Furthermore, this study provides functional evidence that spinal NO plays an important role in the antiallodynic effect of intrathecal clonidine in neuropathic pain.
KW - Acetylcholine
KW - Hyperalgesia
KW - Spinal cord
KW - α-adrenergic receptors
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U2 - 10.1097/00000542-199812000-00031
DO - 10.1097/00000542-199812000-00031
M3 - Article
C2 - 9856728
AN - SCOPUS:0032422242
SN - 0003-3022
VL - 89
SP - 1518
EP - 1523
JO - Anesthesiology
JF - Anesthesiology
IS - 6
ER -