title: Tonic modulation of nociceptive behavior and allodynia by cannabinoid receptors in formalin test in rats.
abstract: Cannabinoids produce anti-nociceptive and anti-hyperalgesic effects in acute, inflammatory and neuropathic pain models. The current study investigated the role of cannabinoid (CB1 and CB2) receptors in modulating formalin-induced nociceptive behavior and mechanical allodynia in the rat. Rats received subcutaneous plantar injections of 5% formalin in the hind paws. Licking, biting and paw flinching nociceptive behaviors were measured 0-60 min after formalin injection. Allodynia was measured at 3 and 6 h, and 1, 3, 5 and 7 days post-injection using the mechanical paw withdrawal threshold. Animals in the experimental group were given i.p. injections of CB1 and CB2 receptor antagonists AM281 and AM630 at a dose of 1 mg/kg concomitant with formalin, and then twice daily for the following 7 days. AM281 and AM630 enhanced nociceptive behaviors, and attenuated the bilateral mechanical paw withdrawal threshold, compared with the vehicle. The results indicate that CB1 and CB2 receptors mediate a tonically inhibitory action on formalin-induced inflammatory pain, especially long-term allodynia, in bilateral hind paws.
authors: Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, People's Republic of China.
authors: Tian-Cheng
authors: TC
authors: Wang
authors: Key Laboratory of Orthopaedics, Disease of Gansu Province, Department of Orthopaedics, the Second Hospital of Lanzhou University, Lanzhou 730030, Gansu, People's Republic of China.
authors: Jing
authors: J
authors: Wang
authors: Key Laboratory of Orthopaedics, Disease of Gansu Province, Department of Orthopaedics, the Second Hospital of Lanzhou University, Lanzhou 730030, Gansu, People's Republic of China.
authors: Xu
authors: X
authors: Xu
authors: Key Laboratory of Orthopaedics, Disease of Gansu Province, Department of Orthopaedics, the Second Hospital of Lanzhou University, Lanzhou 730030, Gansu, People's Republic of China.
authors: Jing-Lin
authors: JL
authors: Ma
authors: Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, People's Republic of China.
authors: Xue-Feng
authors: XF
authors: Wang
mesh_terms: D000818:Animals; D006930:Hyperalgesia / Q000503:physiopathology*; D008297:Male; D059225:Nociception / Q000502:physiology*; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D043882:Receptors, Cannabinoid / Q000502:physiology*
chemical_list: D043882:Receptors, Cannabinoid