Effects of clonidine on pituitary-adrenocortical axis in morphine-tolerant rats and after naloxone-induced withdrawal.
The effects of systemically administered clonidine on pituitary-adrenocortical axis in morphine-tolerant rats and after naloxone-induced withdrawal were examined. In naive animals, clonidine (0.5 and 1 mg/kg s.c.) significantly increased plasma beta-endorphin-like immunoreactivity (beta-END-LI) and cortisol levels. This effect was significantly reduced in morphine-tolerant animals. Naloxone treatment induced an increase of plasma beta-END-LI and cortisol levels in morphine-tolerant animals. The increase in cortisol level after withdrawal was significantly reduced by clonidine. These results are consistent with an interaction between alpha 2-adrenoceptors and opioid systems in the control of pituitary-adrenocortical axis during morphine tolerance and withdrawal.
Vargas
M L
ML
Department of Physiology and Pharmacology, University School of Medicine, Murcia, Spain.
Gonzalvez
M L
ML
Martinez
J A
JA
Arias
L
L
Bruger
A J
AJ
Milanés
M V
MV
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D009021:Morphine Dependence / Q000097:blood*; D009270:Naloxone / Q000009:adverse effects*; D010913:Pituitary-Adrenal System / Q000187:drug effects*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013375:Substance Withdrawal Syndrome / Q000097:blood*; D001615:beta-Endorphin / Q000097:blood
D009270:Naloxone; D001615:beta-Endorphin; D003000:Clonidine; D006854:Hydrocortisone