Chronic stress attenuation of alfa 2 adrenoceptor reactivity is reversed by naltrexone

CANCELA, L.M.; VOLOSIN, M.; MOLINA VICTOR ALEJANDRO

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1988 vol. 31 p. 33 - 33

ow doses of clonidine (50-100 ìg/kg IP) evoke a clear dose-dependent hypoactivity response. Seven daily immobilization sessions prevented the motor activity decrease induced by clonidine. On the contrary, a single stress failed to modify clonidine response. Pretreatment with naltrexone (2 mg/kg IP) fully antagonized the attenuating effect induced by chronic stress on clonidine sedative action. These evidences suggest that chronic but not acute stress reduces the reactivity of á2-adrenoceptors involved in clonidine-induced sedation. In addition, a regulatory mechanism of endogenous opioids seems to participate on á2-adrenoceptors adaptative changes