Involvement of GABA and opioid peptide receptors in sevoflurane-induced antinociception in rat spinal cord.
OBJECTIVE
The spinal cord is pivotal in immobility induced by volatile anesthetics because the anesthetics depress the activity of motor neurons in the spinal cord. The aim of this study was to observe the effects of sevoflurane on pain processing at the spinal level.


METHODS
The firing of the gastrocnemius muscle was evoked by electrical stimulation to the ipsilateral hindpaw in rats. The nociceptive C response of electromyography (EMG) was selected to study. The GABAA receptor antagonist bicuculline (0.1 mg/kg) and opioid receptor antagonist naloxone (0.4 mg/kg) were administered intravenously, either in the presence or in the absence of 1.0% sevoflurane.


RESULTS
In rats with transected spinal cord, sevoflurane produced a profound reduction in the C response in a dose- and time-dependent manner. In the presence of 1.0% sevoflurane, the C responses were increased after injections of bicuculline and naloxone.


CONCLUSIONS
Sevoflurane is a volatile anesthetic that acts directly on the spinal cord to suppress the nociceptive reflex. The sevoflurane-induced suppression of the C response is antagonized by either bicuculline or naloxone. The results suggest that spinal GABAA receptors and opioid peptide receptors are involved in the sevoflurane-induced suppression of spinal nociception.
Wang
Ying-wei
YW
Department of Anesthesiology, Xinhua Hospital, Shanghai Second Medical University, Shanghai 200092, China. wangyingwei@yahoo.com
Deng
Xiao-ming
XM
You
Xin-min
XM
Liu
Shu-xiao
SX
Zhao
Zhi-qi
ZQ
D018685:Anesthetics, Inhalation; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D058787:GABA-A Receptor Antagonists; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects; D009619:Nociceptors / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077149:Sevoflurane; D013116:Spinal Cord / Q000187:drug effects*
D018685:Anesthetics, Inhalation; D058787:GABA-A Receptor Antagonists; D008738:Methyl Ethers; D009292:Narcotic Antagonists; D009270:Naloxone; D000077149:Sevoflurane; D001640:Bicuculline