Antinociception of intrathecal adenosine receptor subtype agonists in rat formalin test.
Adenosine has shown antinociceptive action via spinal adenosine receptors. There are four types of adenosine receptors: A1, A2A, A2B, and A3. We characterized the nature of types of adenosine receptors for the control of nociception at the spinal level. For nociception, formalin solution (5%, 50 microL) was injected into the hindpaw of male Sprague-Dawley rats. The effects of intrathecal adenosine A1 (CPA), A2A (DPMA), and A3 (IB-MECA) receptor agonists were examined. CPA and IB-MECA produced limited or no effect on the early phase response of the formalin test, respectively, but the two drugs depressed the late phase response. DPMA suppressed both phase responses. CPA was the most potent drug among the three in the late phase. These results suggest that spinal adenosine A1 and A2A receptors may be involved in the modulation of the early and the late phase responses of the formalin test, whereas adenosine A3 receptor may be involved in the regulation of the late phase response.
Yoon
Myung Ha
MH
Department of Anesthesiology and Pain Medicine, Chonnam National University, Medical School, Gwangju, Korea.
Bae
Hong Beom
HB
Choi
Jeong Il
JI
D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D007278:Injections, Spinal; D008297:Male; D010147:Pain Measurement; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018047:Receptors, Purinergic P1 / Q000145:classification / Q000502:physiology
D000700:Analgesics; D058906:Purinergic P1 Receptor Agonists; D018047:Receptors, Purinergic P1