In 1997, we described a new automated method of scoring the
pain behaviors in the
formalin test. The algic behavior was automatically measured with the help of a video-analysis system. The time during which the animal grooms, licks, or
bites itself was used as the parameter of
pain. In the present study, we tested various
analgesics to realize a pharmacological validation of the system. The effect of
opiate analgesic (
morphine, i.v.), nonsteroidal anti-inflammatory drugs (
paracetamol, i.v.,
piroxicam, i.v.,
indomethacin, i.v.),
antidepressant drugs (
clomipramine,
desipramine, nortryptyline, and
paroxetine, i.p.), and
serotonin (i.t.) were analyzed. A dose of 1.25 mg/kg of
morphine induced a decrease in the scores of phases 1 and 2.
Naloxone (0.25 mg/kg) reversed the effect of
morphine (2.5 mg/kg). A 20-mg/kg dose of
indomethacin induced a decrease in the second phase, and
paracetamol induced a decrease in both phases (
analgesic doses were 400 mg/kg and 200 mg/kg for first and second phases, respectively).
Piroxicam had no effect on the
pain scores.
Clomipramine,
desipramine, and
paroxetine at a dose of 5 mg/kg induced a significant decrease in the second phase.
Nortriptyline had no effect on the
pain scores. A dose of 75 microg of
serotonin induced a decrease in both phases 1 and 2. This study demonstrated that this system shows a good pharmacological sensitivity, although it is lower than that of manual assessment.