Involvement of dynorphin A in the inhibition of morphine physical dependence by N-nitro-L-arginine in rats.
OBJECTIVE
To investigate the involvement of immunoreactive-dynorphin A in the inhibitory effect of N-nitro-L-arginine on the morphine physical dependence in rats.


METHODS
The rats were rendered dependent on morphine by subcutaneous administration of morphine solution three times daily in a manner of dose increment of 5 mg.kg(-1) for 6 days. The degree of morphine physical dependence was monitored by scoring the abstinence syndromes precipitated by 5 mg.kg(-1) naloxone of the rats. The expression levels of immunoreactive dynorphin A in tissues were determined using a radioimmunoassay.


RESULTS
Intraperitoneal injection of 5 mg.kg(-1) N-nitro-L-arginine suppresses most of the withdrawal symptoms of morphine dependent rats. N-nitro-L-arginine can elevate the expression of immunoreactive dynorphin.


CONCLUSIONS
Chronic N-nitro-L-arginine administration can inhibit the development of morphine physical dependence in a manner of dose-dependence, which is significantly related to its role of regulating the endogeneous dynorphin system.
Wan
Xingwang
X
International Co-operation Laboratory, Eastern Hepatobiliary Surgery Institute, Second Military Medical University, Shanghai 200438, China.
Huang
Mao
M
He
Yaqin
Y
Li
Wanhai
W
You
Zhendong
Z
Lu
Changlin
C
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000502:physiology*; D008297:Male; D009021:Morphine Dependence / Q000517:prevention & control*; D019335:Nitroarginine / Q000493:pharmacokinetics* / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D019335:Nitroarginine; D004399:Dynorphins