Tail-flick test

To evaluate the Mor analgesic, a tail-flick analgesia meter apparatus (UGO BASILE, Italy) was used (9). This apparatus was set to shine a light beam focused on the animal tail’s ventral part. The heat intensity was adjusted to elicit 2-4 s baseline responses. The time between tail exposure to radiant heat and tail withdrawal was considered tail-flick latency. To avoid tissue damage (cut-off point = 10 s), the heat stimulus was discontinued after 10 s. Before the tail-flick test, the animals were habituated to laboratory surroundings. During the test, the mice were lightly restrained in a Plexiglas mice restrainer box. Through gaps located in the restrainer’s interior door, the mice's tail was exposed. To reduce mice stress during the assessment, they were habituated to the test conditions for 3 days before the first trial. Results are expressed as %MPE, which was calculated according to the following equation:

where T0 is pre-treatment latency; T1 is post-treatment latency; and T2 is the cut-off time.