Effects of codeine, naproxen and dexamethasone on formalin-induced pain in the naked mole-rat.
A dilute solution of formalin (20 microliters of 10% formalin) was injected subcutaneously in the dorsal right hind paw of the naked mole-rat. The injection of the dilute formalin produced two periods of pain behaviour, the early (0-5 minutes) and the late phase (25-60 minutes). These were quantified as the total time spent licking the injected paw. Codeine phosphate (10, 25 or 50 mg kg-1) significantly reduced pain behaviour in both the early and late phase. Codeine administration also induced aggressive, hyperactive behaviour and motor impairment that was naloxone (2 mg kg-1) reversible. Naproxen (200 mg kg-1) and dexamethasone phosphate (30 mg kg-1) significantly reduced licking activity in the late phase only.
Karim
F
F
Department of Animal Physiology, University of Nairobi, Kenya.
Kanui
T I
TI
Mbugua
S
S
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003061:Codeine / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005557:Formaldehyde; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D009127:Muscle Rigidity / Q000139:chemically induced; D009270:Naloxone / Q000494:pharmacology; D009288:Naproxen / Q000494:pharmacology*; D010146:Pain / Q000139:chemically induced / Q000517:prevention & control*; D012377:Rodentia / Q000502:physiology*
D005557:Formaldehyde; D009270:Naloxone; D009288:Naproxen; D003907:Dexamethasone; D003061:Codeine