Effect of opioid agonist-antagonist interaction on morphine dependence in rats.
Morphine dependence was induced by treatment with morphine-admixed food (0.25mg/g of food) for 7 days. Withdrawal was precipitated by injecting naloxone (0.5mg/kg, s.c.). Rats treated with morphine exhibited body weight loss upon the naloxone injection. When morphine-dependent rats were injected subcutaneously with morphine, codeine, meperidine and pentazocine 30 min before the naloxone injection, these drugs significantly suppressed the naloxone-precipitated loss of body weight in a dose-dependent manner. However, body weight loss induced through coadministration of naloxone and Mr-2266 BS were not suppressed by morphine pretreatment. These results suggest that opioids protect against naloxone-precipitated loss of body weight, and that mu and kappa opiate receptors play an important role in the protection against naloxone-precipitated withdrawal.
Suzuki
T
T
Department of Pharmacology, Hoshi University, Tokyo, Japan.
Fukagawa
Y
Y
Yoshii
T
T
Yanaura
S
S
D000818:Animals; D001575:Benzomorphans / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D003061:Codeine / Q000494:pharmacology; D008297:Male; D008614:Meperidine / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology*; D010423:Pentazocine / Q000494:pharmacology; D051381:Rats; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*; D019966:Substance-Related Disorders / Q000503:physiopathology*
D001575:Benzomorphans; D009270:Naloxone; C027247:MR 2266; D009020:Morphine; D008614:Meperidine; D010423:Pentazocine; D003061:Codeine