ANTINOCICEPTIVE EFFECTS INDUCED BY DIAZEPAM AT DIFFERENT AGES

The aim of this study was to investigate age-related effects of diazep am on the antinociceptive tail-flick response. Female Wistar rats were tested in a tail-flick apparatus. Diazepam (5.0 mg kg(-1) or 7.5 mg k g(-1)) or its vehicle were given intraperitoneally, 60 min prior to th e test. Among the vehicle-treated animals, 60-day-old animals showed a higher tail-flick latency (TFL) than 20- or 30-day-old animals. 20- a nd 30-day-old animals treated with diazepam 7.5 mg kg(-1) had a higher TFL than those given vehicle or diazepam 5.0 mg kg(-1) 60-day-old ani mals treated with diazepam 5.0 mg kg(-1) or 7.5 mg kg(-1) had a higher TFL than the vehicle-treated group. The results show that 20- and 30- day-old female rats are more sensitive than 60-day-old animals to the tail-flick response and less responsive to the antinociceptive effect induced by diazepam.