Evaluation of the Antinociceptive Effect

The behavioral tests were performed between 9:00 am and 4:00 pm. To assess the mechanical nociceptive threshold, we used the rat paw pressure test [35] (Ugo Basile, VA, Italy). The pressure was recorded before and for up to 192 h after the crotalphine treatment or PGE2 injection. Testing was conducted blind to the group designation. To reduce stress, the rats were habituated to the testing procedure a day before experimentation. In this test, an increasing amount of force (measured in g) was applied to the hind paw of the rat and interrupted when the animal withdrew the paw. The force necessary to induce this reaction was recorded as the mechanical nociceptive threshold. A maximum pressure of 250 g (i.e., cut-off) was established to avoid damage to the paw.
