Roles of adenosine receptor subtypes in the antinociceptive effect of intrathecal adenosine in a rat formalin test.
The contributions of adenosine receptor subtypes to antinociception produced by adenosine were determined at the spinal level. There are 4 types of adenosine receptors, namely A1, A(2A), A(2B) and A3. The authors investigated the properties of the subtypes of spinal adenosine receptors in terms of nociceptive modulation. The nociceptive state was induced by subcutaneously injecting formalin solution (5%, 50 microl) into the hind paws of male Sprague-Dawley rats. After observing the effect of intrathecal adenosine during the formalin test, the effects of intrathecal adenosine A1 (CPT), A(2A) (CSC), A(2B) (alloxazine) and A3 (MRS 1220) receptor antagonists on the action of adenosine were examined. Intrathecal adenosine inhibited phase 2 flinching response without affecting phase 1 response. CPT, CSC, alloxazine and MRS 1220 antagonized the antinociceptive action of adenosine during phase 2 of the formalin test. These results suggest that spinal adenosine A1, A(2A), A(2B) and A3 receptors may play an important role in the antinociception of adenosine in the formalin-induced facilitated state.
Yoon
Myung Ha
MH
Department of Anesthesiology and Pain Medicine, Chonnam National University, Medical School, Gwangju, Korea. mhyoon@chonnam.ac.kr
Bae
Hong Beom
HB
Choi
Jeong Il
JI
Kim
Seok Jai
SJ
Chung
Sung Tae
ST
Kim
Chang Mo
CM
D000241:Adenosine / Q000008:administration & dosage*; D000700:Analgesics / Q000008:administration & dosage*; D000818:Animals; D007278:Injections, Spinal; D010147:Pain Measurement; D051381:Rats; D018047:Receptors, Purinergic P1 / Q000145:classification / Q000502:physiology*
D000700:Analgesics; D018047:Receptors, Purinergic P1; D000241:Adenosine