Effects of intrathecal naloxone and atropine on the nociceptive suppression induced by norepinephrine and serotonin at the spinal level in rats.
The interrelations among norepinephrine (NE), serotonin (5-HT), opiate-like substances (OLS), and acetylcholine (ACh) were investigated by using electrophysiological method combining with intrathecal (i.t.) injection. The results show that: (1) pretreatment with i.t. naloxone (Nal) completely reversed the NE-induced suppression of nociceptive discharges in parafascicular (PF) neurons, but partially reversed that of induced by i.t. 5-HT; (2) pretreatment with i.t. atropine (Atr) completely reversed the suppression induced by either NE or 5-HT. The results suggest that OLS may act as a necessary mediator for NE-induced suppression on the spinal transmission of nociceptive inputs, while it is only partially involved in the 5-HT-induced suppression, and moreover, that endogenous ACh is necessary for the performance of nociceptive suppression induced by either spinal NE or 5-HT administration.
Li
Y J
YJ
Department of Neurobiology, Shanxi Medical College, Taiyuan, People's Republic of China.
Zhang
Z H
ZH
Chen
J Y
JY
Qiao
J T
JT
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology*; D004723:Endorphins / Q000502:physiology; D007278:Injections, Spinal; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D009619:Nociceptors / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010812:Physical Stimulation; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects*
D004723:Endorphins; D012702:Serotonin Antagonists; D012701:Serotonin; D009270:Naloxone; D001285:Atropine; D000109:Acetylcholine; D009638:Norepinephrine