2.5. Analgesic effect of propofol in chicks
Thirty two chicks were randomly divided into four
groups of eight birds each. The chicks were injected with
either physiological saline solution (control) or with propofol
at 1, 2 and 4 mg/kg. The highest dose of propofol
was almost two-fold of the analgesic ED50 of the drug.
For each chick, we measured the minimum voltage that
caused aversive pain response, as mentioned in the previous
experiment, before propofol injection and then 15 min
after the injection. The increase in the voltage in each
group was assessed statistically to determine the analgesic
response of the chicks to propofol.
Using another analgesic-anti-inflammatory protocol, 24
chicks were randomly divided into three groups of eight
birds each. Pain and inflammatory responses were induced
in the chicks by injecting 0.05 ml of 0.1% aqueous solution
of formalin into the planter region of the right foot
[37,38]. The planter of the left foot was injected with physiological
saline solution (0.05 ml) as a control measure. The
chicks were treated with either physiological saline solution
(control) or with propofol at 2 and 4 mg/kg 15 min
before the formalin injection. Immediately after the formalin
injection, we recorded within 3 min the latency to lift
the right foot and the frequency of lifting the right foot in
response to formalin injection. Further, we determined the
anti-inflammatory effect of propofol by measuring the foot
thickness (mm) with an electronic digital caliber (Electronics
Lab, China) before and 1 h after the formalin injection.
The anti-inflammatory response (%) was calculated as follows: