2.3.3. hot plate test

A transparent rectangular jar was placed on the apparatus covering the hot plate along its perimeter. The metal surface and the jar were cleaned with 70% ethanol before experiments. The hot plate apparatus (MOD 35D Hot plate) was switched on and left to warm to 63°C ± 1.0 before the experiments commenced. The sampled animal was put on the plate facing away from the investigator and simultaneously the stopwatch was started to measure the time latency to display of feet rubbing, alternating hind feet, escape or raising plastron. The stopwatch was stopped after the animal displayed the first nociceptive behaviour. The animal was then withdrawn from the hot plate apparatus. The cut‐off time was set at 3 minutes. In the absence of any reaction, 3 minutes were considered as latency by default. The hot plate was cleaned with water and 70% ethanol before testing another animal. All the animals were given a baseline test to establish that they had similar sensitivities to thermal nociception prior to the drug injection. All experiments were performed at a room temperature of 24–25°C, and between 10.00 a.m. and 5.00 p.m.