Inhibitory effect of crotoxin on the pain-evoked discharge of neurons in thalamic parafascicular nucleus in rats.
Crotoxin (Cro), the principal neurotoxic component of Crotalus durissus terrificus, has been previously reported to have a behavioral analgesic effect in rats and mice. The present study investigated electrophysiologically the effect of Cro on pain-evoked unit discharge of neurons in thalamic parafascicular nucleus (Pf) and underlying mechanisms of its effect. The electrical discharge of Pf neurons was recorded with the microelectrode technique in rats. Intracerebroventricular (i.c.v.) injection of Cro at 0.25, 0.45 and 0.65 microg/kg resulted in a dose-dependent inhibitory effect on the pain-evoked discharge of Pf neurons. The discharge frequency and the discharge duration significantly (P<0.05) decreased after Cro administration. This inhibitory effect was significantly (P<0.05) attenuated after pretreatment with para-chlorophenylalanine (pCPA), or electrolytic lesion of dorsal raphe (DR) nucleus. In contrast, i.c.v. injection of atropine (muscarinic receptor antagonist, 5 microg) or naloxone (opioid receptor antagonist, 4 microg) had no effect on Cro-induced inhibition of discharge of Pf neurons. The results suggested that Cro has an analgesic effect, which is mediated, at least partially, by the central serotonergic system.
Zhu
Qi
Q
Department of Neurobiology, School of Medicine, Soochow University, Ren-Ai Road, Dushu Lake Campus, Suzhou Industrial Park, Suzhou 215123, PR China.
Wu
Dian-Chen
DC
Zhou
Xi-Ping
XP
Gong
Shan
S
Cheng
Bo-Chao
BC
Qin
Zheng-Hong
ZH
Reid
Paul F
PF
Yin
Qi-Zhang
QZ
Jiang
Xing-Hong
XH
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003439:Crotoxin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D020646:Intralaminar Thalamic Nuclei / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010146:Pain / Q000188:drug therapy* / Q000503:physiopathology*; D010276:Parasympatholytics / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000700:Analgesics; D009292:Narcotic Antagonists; D010276:Parasympatholytics; D009270:Naloxone; D001285:Atropine; D003439:Crotoxin