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Effect of locus coeruleus stimulation on unit discharge of hypothalamic arcuate nucleus in rats

Yu Guangdi, Chen Jinsong, Yin Weiping, Yin Qizhang

Laboratory of Electrophysiology, Suzhou Medical College. Suzhou, Jiangsu, China

Abstract

Previous studies in our laboratory have shown that hypothalamic arcuate nucleus (ARC) and locus coeruleus (LC) play an important role in pain modulation and acupuncture analgesia. In the present experiment the effect of LC stimulation on unit discharges of ARC in immobilized rats were examined. The response of ARC units to LC stimulation was inhibitory in nature (23 among 38 units), while the response of ARC units to peripheral noxious stimulation was predominantly excitatory (20 among 27 units). LC stimulation could shorten the duration of noxious response of ARC units, i.e. depress their noxious response. Pharmacological analysis indicated that #alpha#_(2)-agonist (clonidine) and #alpha#_(1)-antagonist (phenoxybenzamine) could increase the average rate of discharge of ARC unit, while #beta#-agonist (isoprenaline) and #beta#-antagonist (propranolol) showed no effects. These results suggest that the effect of noradrenergic neurons of LC on ARC neurons might be mediated by #alpha#-receptors.

Key words: Hypothalamic arcuate nucleus;Locus coeruleus;Pain;Clonidine;Phenosybenzamine;Isoprenaline;Propranolol

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Citing This Article：

Yu Guangdi, Chen Jinsong, Yin Weiping, Yin Qizhang. Effect of locus coeruleus stimulation on unit discharge of hypothalamic arcuate nucleus in rats. Acta Physiol Sin 1985; 37 (2): (in Chinese with English abstract).