ArticlesCharacterization of Δ9-Tetrahydrocannabinol and Anandamide Antinociception in Nonarthritic and Arthritic Rats
Section snippets
Animals
Male Sprague–Dawley rats (Harlan Laboratories, Indianapolis, IN), which weighed 250–300 g, were housed in the animal care quarters maintained at 22 ± 2°C on a 12 L:12 D cycle. Food and water were available ad lib. The rats were brought to a test room (at 22 ± 2°C) on the day of testing. All experiments were conducted according to guidelines established by the Institutional Animal Care and Use Committee of the Medical College of Virginia.
Freund’s Adjuvant Treatment
A volume of 0.5 ml of vehicle (85:15 paraffin oil:Arlacel
Results
Experiments were conducted to test the hypothesis that THC elicits antinociception in the paw-pressure test in nonarthritic and arthritic rats. Before conducting the THC experiments, it was necessary to demonstrate that the treatment with Freund’s complete adjuvant caused a significant reduction in paw pressure threshold (Table 1). These results indicate that the arthritic rats were significantly more sensitive to mechanical nociception than nonarthritic rats. In nonarthritic rats (Fig. 1A),
Discussion
The results of this study indicate that THC and anandamide elicited significant antinociception in the paw-pressure test in nonarthritic rats. THC had a rapid onset and long duration of action. Early studies by Sofia et al. [40]also established that THC (PO) is effective in the rat paw pressure test, as well as the Haffner tail-pinch test in mice. In another study, the synthetic cannabinoid WIN 55,212-2 in anesthetized rats effectively blocked the response of wide dynamic range dorsal spinal
Acknowledgements
This work was supported by the National Institute on Drug Abuse Grants: DA05274, DA09789, DA03672, and K02-00186. We wish to thank Dr. Billy R. Martin, Department of Pharmacology and Toxicology, Medical College of Virginia, for his assistance and collaboration on this project.
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