Immunofluorescent spectral analysis reveals the intrathecal cannabinoid agonist, AM1241, produces spinal anti‐inflammatory cytokine responses in neuropathic rats exhibiting relief from allodynia

• Published in: Brain and behavior 2012-03, Vol.2 (2), p.155-177
• Main Authors: Wilkerson, Jenny L., Gentry, Katherine R., Dengler, Ellen C., Wallace, James A., Kerwin, Audra A., Kuhn, Megan N., Zvonok, Alexander M., Thakur, Ganesh A., Makriyannis, Alexandros, Milligan, Erin D.
• Format: Article
• Language: English
• Subjects: Analgesics; CCI; Cytokines; DRG; Drug dosages; Kinases; Light; MAGL; Original Research; Pain; paraffin immunohistochemistry; Peripheral neuropathy; Proteins; Rodents; Spinal cord; Tumor necrosis factor-TNF
• ISSN: 2162-3279; 2162-3279
• DOI: 10.1002/brb3.44

During pathological pain, the actions of the endocannabinoid system, including the cannabinoid 2 receptor (CB2R), leads to effective anti‐allodynia and modifies a variety of spinal microglial and astrocyte responses. Here, following spinal administration of the CB2R compound, AM1241, we examined immunoreactive alterations in markers for activated p38 mitogen‐activated protein kinase, interleukin‐1β (IL‐1β), the anti‐inflammatory cytokine, interleukin‐10 (IL‐10) as well as degradative endocannabinoid enzymes, and markers for altered glial responses in neuropathic rats. In these studies, the dorsal horn of the spinal cord and dorsal root ganglia were examined. AM1241 produced profound anti‐allodynia with corresponding immunoreactive levels of p38 mitogen‐activated kinase, IL‐1β, IL‐10, the endocannabinoid enzyme monoacylglycerol lipase, and astrocyte activation markers that were similar to nonneuropathic controls. In contrast, spinal AM1241 did not suppress the increased microglial responses observed in neuropathic rats. The differences in fluorescent markers were determined within discrete anatomical regions by applying spectral analysis methods, which virtually eliminated nonspecific signal during the quantification of specific immunofluorescent intensity. These data reveal expression profiles that support the actions of intrathecal AM1241 control pathological pain through anti‐inflammatory mechanisms by modulating critical glial factors, and additionally decrease expression levels of endocannabinoid degradative enzymes. Spinal AM1241 reverses allodynia with corresponding anti‐inflammatory effects in the spinal cord and dorsal root ganglia. Additionally, spinal AM1241 modulated levels of the endocannabinoid degradative enzyme MAGL within the dorsal horn spinal cord.