Kynurenic acid enhances electroacupuncture analgesia in normal and carrageenan-injected rats.
The interaction between electroacupuncture (EA) and an intrathecally administered wide-spectrum excitatory amino acid (EAA) receptor(s) antagonist, kynurenic acid (KYNA) on carrageenan-induced thermal hyperalgesia and spinal Fos expression was investigated. Intrathecal (i.t.) injection of 0.1, 1, 10, and 100 nmol KYNA markedly and dose-dependently increased the latency of paw withdrawal (PWL) of the carrageenan-injected paw. While the PWLs of the non-injected and normal saline (NS)-injected paws were not obviously affected by application of KYNA at the doses tested. Intrathecal injection of 0.1 nmol KYNA significantly potentiated the anti-nociception induced by EA stimulation of contralateral 'Zu-San-Li' and 'Kun-Lun' acupoints either in the carrageenan- or NS-injected rats. Three hours after intraplantar (i.pl.) injection of carrageenan, the number of Fos-like immunoreactive (Fos-LI) neurons was significantly increased in all layers of ipsilateral spinal cord at L(4)-L(5) with the higher density in laminae I-II and V-VI. Intrathecally pre-administered KYNA (10 nmol) significantly reduced the total number of carrageenan-induced Fos-LI neurons with more apparent reduction in laminae I-II and IV-V. Pre-coapplication of 10 nmol KYNA and EA of bilateral 'Zu-San-Li' and 'Kun-Lun' acupoints, the numbers of carrageenan-induced Fos-LI neurons in laminae I-II and V-VI further reduced. The level of Fos expression in the spinal cord induced by carrageenan was significantly lower compared with that of i.t. injection of KYNA or EA alone. These results demonstrated that EAA receptor(s) antagonist could enhance EA-induced anti-nociception and anti-hyperalgesia.
Zhang
Yu-Qiu
YQ
Institute of Neurobiology, Fudan University, 220 Han Dan Road, 200433, Shanghai, China. yuqzhang@fudan.edu.cn
Ji
Guang-Chen
GC
Wu
Gen-Cheng
GC
Zhao
Zhi-Qi
ZQ
D000818:Animals; D002351:Carrageenan; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015671:Electroacupuncture / Q000379:methods*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D006930:Hyperalgesia; D007150:Immunohistochemistry; D007736:Kynurenic Acid / Q000494:pharmacology*; D008297:Male; D016761:Oncogene Proteins v-fos / Q000187:drug effects / Q000378:metabolism*; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology; D059408:Pain Management; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors
D018691:Excitatory Amino Acid Antagonists; D016761:Oncogene Proteins v-fos; D002351:Carrageenan; D007736:Kynurenic Acid