Formalin-induced pain antagonizes the development of opiate dependence in the rat.
Clinical studies have suggested that patients who take morphine for pain relief do not show a high degree of dependence. The present study examined the development of naloxone-precipitated withdrawal in rats receiving morphine in the presence or absence of formalin-induced pain. Morphine (10 mg/kg, i.p.) or saline was administered for 4 consecutive days 10 min after a subcutaneous injection of 50 microliters of 2.5% formalin or saline into the hind-paw. On the 5th day, rats were injected with naloxone (1 mg/kg, i.p.) and observed for signs of precipitated withdrawal (ptosis, teeth chattering and excretion/diarrhea). Naloxone-precipitated withdrawal symptoms were significantly greater in rats that received morphine in the absence of pain than in rats that received morphine in the presence of pain.
Vaccarino
A L
AL
Department of Psychology, University of New Orleans, Lakefront, LA 70148.
Couret
L C
LC
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001763:Blepharoptosis / Q000139:chemically induced; D003967:Diarrhea / Q000139:chemically induced / Q000503:physiopathology; D005557:Formaldehyde / Q000494:pharmacology*; D008297:Male; D009021:Morphine Dependence / Q000503:physiopathology / Q000517:prevention & control* / Q000523:psychology; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology*; D051381:Rats; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology / Q000523:psychology
D005557:Formaldehyde; D009270:Naloxone