Ketamine potentiates the effect of electroacupuncture on mechanical allodynia in a rat model of neuropathic pain.
Mu-opioid agonists and N-methyl-d-aspartate (NMDA) receptor antagonists have been shown to attenuate mechanical allodynia in neuropathic pain models. We have previously reported that 2Hz electroacupuncture (EA) produced analgesia via releasing endogenous opioid peptides (i.e. beta-endorphin and endomorphin) and the activated micro-opioid receptors. The present study aimed to examine whether ketamine, an NMDA receptor antagonist, can enhance the anti-allodynic effects induced by 2Hz EA in a rat model of neuropathic pain following spinal nerve ligation (SNL). The results are as follows: (1) EA itself or i.p. injection of ketamine reduced mechanical allodynia (i.e. increase in withdrawal threshold). (2) Although injection of ketamine at a low dose (1.0mg/kg) alone did not influence mechanical withdrawal threshold, combination of ketamine at this dose with EA produced more potent anti-allodynic effect than that induced by EA alone. (3) The anti-allodynic effect of EA combined with ketamine could be reversed by i.p. injection of naloxone (2.0 mg/kg). These results suggested that ketamine potentiate the anti-allodynic of EA in rats with spinal nerve ligation, and endogenous opioid system is likely to be involved in this process.
Huang
Cheng
C
Key Laboratory of Neuroscience, Neuroscience Research Institute, Peking University, 38 Xueyuan Road, Beijing 100083, PR China.
Li
Han-Ting
HT
Shi
Yu-Shun
YS
Han
Ji-Sheng
JS
Wan
You
Y
D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015671:Electroacupuncture / Q000379:methods*; D005260:Female; D007649:Ketamine / Q000494:pharmacology / Q000627:therapeutic use*; D010146:Pain / Q000188:drug therapy*; D059408:Pain Management; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D013127:Spinal Nerves / Q000293:injuries
D007649:Ketamine