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#Beta#-endorphin and dynorphin are involved in the central depressor action of clonidine or norepinephrine in rats

Xie Cuiwei, Han Jisheng

Depa,tment of Physiology, Beijing Medical College. Beijing, China

Abstract

Intracerebroventricular injection (icv) of clonidine or norepinephrine (NE) induced significant depressor and bradycardiac responses in rats, which were partly antagonized by icv a-adrenoceptor blocker phentolamine. These responses were found to be blocked by large doses of naloxone (100 #mu#g, icv; 10 mg/kg, iv), but not by small doses(10 #mu#g, icv; 2 mg/kg, iv). Antibodies directed to #beta#-endorphin, dynorphin, met-enkephalin and leu-enkephalin, respectively, were injected icv prior to the administration of clonidine or NE. Significant reversal of the depressor action of clonidine or NE was seen in rats pretreated with #beta#-endorphin or dynorphin antibody, while antibodies against met-enkephalin and leu-enkephalin were not effective. The results imply that an activation of #alpha#-receptor as well. as the release of #beta#-endorphin and dynorphin in the brain are important for mediating the depressor action of icv clonidine or NE.

Key words: Clonidine;Norepinephrine;Intracerebroventricular injection;Depressor action;Naloxone;Beta-endorphin antibody;Dynorphin antibody

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Citing This Article：

Xie Cuiwei, Han Jisheng. #Beta#-endorphin and dynorphin are involved in the central depressor action of clonidine or norepinephrine in rats. Acta Physiol Sin 1985; 37 (2): (in Chinese with English abstract).