Effects of electroacupuncture on cold allodynia in a rat model of neuropathic pain: mediation by spinal adrenergic and serotonergic receptors.
The present study was performed to examine the effects of electroacupuncture (EA) on cold allodynia and its mechanisms related to the spinal adrenergic and serotonergic systems in a rat model of neuropathic pain. For the neuropathic surgery, the right superior caudal trunk was resected at the level between S1 and S2 spinal nerves innervating the tail. Two weeks after the nerve injury, EA stimulation (2 or 100 Hz) was delivered to Zusanli (ST36) for 30 min. The behavioral signs of cold allodynia were evaluated by the tail immersion test [i.e., immersing the tail in cold water (4 degrees C) and measuring the latency to an abrupt tail movement] before and after the stimulation. And then, we examined the effects of intrathecal injection of prazosin (alpha1-adrenoceptor antagonist, 30 microg), yohimbine (alpha2-adrenoceptor antagonist, 30 microg), NAN-190 (5-HT1A antagonist, 15 microg), ketanserin (5-HT2A antagonist, 30 microg), and MDL-72222 (5-HT3 antagonist, 12 microg) on the action of EA stimulation. Although both 2 Hz and 100 Hz EA significantly relieved the cold allodynia signs, 2 Hz EA induced more robust effects than 100 Hz EA. In addition, intrathecal injection of yohimbine, NAN-190, and MDL-72222, but not prazosin and ketanserin, significantly blocked the relieving effects of 2 Hz EA on cold allodynia. These results suggest that low-frequency (2 Hz) EA is more suitable for the treatment of cold allodynia than high-frequency (100 Hz) EA, and spinal alpha2-adrenergic, 5-HT1A and 5-HT3, but not alpha1-adrenergic and 5-HT2A, receptors play important roles in mediating the relieving effects of 2 Hz EA on cold allodynia in neuropathic rats.
Kim
Sun Kwang
SK
Department of East-West Medicine, Graduate School, Kyung-Hee University, Dongdaemoon-Gu, Seoul, South Korea.
Park
Jung Hyuk
JH
Bae
Sang Jin
SJ
Kim
Ji Hoon
JH
Hwang
Byung Gil
BG
Min
Byung-Il
BI
Park
Dong Suk
DS
Na
Heung Sik
HS
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D003080:Cold Temperature / Q000009:adverse effects; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D015671:Electroacupuncture; D006941:Hyperesthesia / Q000628:therapy*; D008297:Male; D059408:Pain Management; D010147:Pain Measurement / Q000379:methods; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000503:physiopathology / Q000528:radiation effects; D013997:Time Factors; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D015016:Yohimbine; D011224:Prazosin