[Phentolamine antagonizes the effects of norepinephrine on the activity of pain-related neurons in the parafascicular nucleus of morphine-dependent rats].
OBJECTIVE
To examine the antagonization of phentolamine against the effects of norepinephrine (NE) on the activity of pain-related neurons in the parafascicular nucleus of morphine-dependent rats.


METHODS
Electric impulses were applied as nociceptive stimulus to the right sciatic nerve of morphine-dependent rats, and the discharges of the pain-related neurons in the parafascicular nucleus were recorded by extracellular recording method with glass microelectrodes.


RESULTS
Intracerebroventricular injection of norepinephrine resulted in the inhibition of evoked response of the pain-excited neurons as well as the excitation of evoked response of the pain-inhibiting neurons. Both the inhibitory effect on the electric discharges of the pain-excited neurons and the excitatory effect on the pain-inhibiting neurons of norepinephrine were almost completely blocked by intracerebroventricular administration of phentolamine.


CONCLUSIONS
Phentolamine antagonizes the inhibitory effect of norepinephrine on the activity of pain-related neurons in the parafascicular nucleus in morphine-dependent rats, and norepinephrine may play an important role in the integration of the pain signal through the alpha-receptors.
Jin
Xiu-dong
XD
Department of Physiology, Mudanjiang Medical College, Mudanjiang 157011, China. md-guan@163.com
Guan
Yan-zhong
YZ
Zhang
Shu-jie
SJ
Xu
Man-ying
MY
Yue
Wen-jie
WJ
D000818:Animals; D004336:Drug Antagonism; D004594:Electrophysiology; D020646:Intralaminar Thalamic Nuclei / Q000166:cytology / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects*; D009638:Norepinephrine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D010646:Phentolamine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D009638:Norepinephrine; D010646:Phentolamine