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. 2010 Sep 16:6:56.
doi: 10.1186/1744-8069-6-56.

Evaluation of phenoxybenzamine in the CFA model of pain following gene expression studies and connectivity mapping

Meiping Chang  1 , Sarah Smith, Andrew Thorpe, Michael J Barratt, Farzana Karim
Affiliations

Evaluation of phenoxybenzamine in the CFA model of pain following gene expression studies and connectivity mapping

Meiping Chang et al. Mol Pain. .

Abstract

Background: We have previously used the rat 4 day Complete Freund's Adjuvant (CFA) model to screen compounds with potential to reduce osteoarthritic pain. The aim of this study was to identify genes altered in this model of osteoarthritic pain and use this information to infer analgesic potential of compounds based on their own gene expression profiles using the Connectivity Map approach.

Results: Using microarrays, we identified differentially expressed genes in L4 and L5 dorsal root ganglia (DRG) from rats that had received intraplantar CFA for 4 days compared to matched, untreated control animals. Analysis of these data indicated that the two groups were distinguishable by differences in genes important in immune responses, nerve growth and regeneration. This list of differentially expressed genes defined a "CFA signature". We used the Connectivity Map approach to identify pharmacologic agents in the Broad Institute Build02 database that had gene expression signatures that were inversely related ('negatively connected') with our CFA signature. To test the predictive nature of the Connectivity Map methodology, we tested phenoxybenzamine (an alpha adrenergic receptor antagonist) - one of the most negatively connected compounds identified in this database - for analgesic activity in the CFA model. Our results indicate that at 10 mg/kg, phenoxybenzamine demonstrated analgesia comparable to that of Naproxen in this model.

Conclusion: Evaluation of phenoxybenzamine-induced analgesia in the current study lends support to the utility of the Connectivity Map approach for identifying compounds with analgesic properties in the CFA model.

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Figures

Figure 1
Figure 1
Oral naproxen is effective in reducing nociceptive behavior in 4 day CFA-injected rats. Naproxen reduced A) mechanical thresholds and B) paw withdrawal latencies taken 2 hr post dose. n = 6-16 rats per group. For this and other figures, data is presented as mean +/- s.e.m. **p < 0.01 and ***p < 0.001, significant differences from vehicle (saline) - dosed rats.
Figure 2
Figure 2
Heat map of transcripts differentially expressed in the DRG between naïve and CFA injected rats. The branch length in the dendrogram represents the relation between the samples, the shorter the branch, the higher the similarity between the samples. Up-regulated genes are shown in yellow and down-regulated genes are in blue.
Figure 3
Figure 3
The eicosanoid signaling pathway from Ingenuity Pathway Analysis software. Only part of the pathway is shown. The highlighted genes (in yellow) were down-regulated in the 4 day CFA model of inflammatory pain. PLA2: phospholipase A2 group IVA; PTGS: prostaglandin-endoperoxide synthase 1; ALOX12, ALOX15: rat arachidonate 12/15-lipoxygenase.
Figure 4
Figure 4
Compounds identified following connectivity mapping of the CFA signature.
Figure 5
Figure 5
Effect of oral phenoxybenzamine administered to rats on day 4 of the CFA model of inflammatory pain. Mechanical thresholds were read 2 hours post-dosing. n = 8-15 per group. *p < 0.05 and **p < 0.01, significant differences from vehicle (saline) - dosed rats.
See this image and copyright information in PMC

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