Dose-dependent analgesic and hyperalgesic effects of systemic naloxone in arthritic rats.
The effects of various i.v. naloxone doses (10 microgram, 300 microgram, 600 microgram, 1 mg/kg) were studied upon vocalization threshold to foot-pressure in 30 normal rats and 70 rats with Freund's adjuvant-induced arthritis. In arthritic rats, the lowest naloxone doses yielded a clear increase in pressure required to trigger vocalization (i.e. were analgesic) while the highest dose (1 mg/kg) was hyperalgesic. In normal rats, naloxone never induced significant changes in the vocalization threshold.
D000818:Animals; D001168:Arthritis / Q000188:drug therapy*; D001169:Arthritis, Experimental / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009270:Naloxone / Q000627:therapeutic use*; D009619:Nociceptors / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds
D009270:Naloxone