Background and aims: Adult zebrafish (Danio rerio) has been proposed as a low-cost and simple alternative to the use of higher vertebrates in laboratory research on novel compounds with antinociceptive potential. This study aimed to investigate the orofacial nociceptive response induced by cinnamaldehyde in adult zebrafish, observing environmental changes. 
Methods: Cinnamaldehyde (0.33 µM, 5.0 µL) was applied to the lips of the animals (n=8/group) 30 min after pre-treated (20 µL;i.p) with vehicle (saline) or morphine (5.0 mg/mL). Naive groups (n=8/each) were included. After the applications of the cinnamaldehyde, the animals were transferred to the Petri dishes (10x15cm) or beaker (250mL) and the orofacial nociception was quantified in terms of locomotor activity (0-5min). In another set of experiments, it was evaluated whether acclimatization of animals 24h before the experiments would alter the nociceptive response to cinnamaldehyde. The influence of experiment period (morning or afternoon) was also analyzed. All experimental procedures were approved by the Ethics Committee for the Use of Animals of the State University of Ceará (#7210149/2016). 
Results: The fact that the experiment was carried out on the Petri dish or the beaker did not alter the response to cinnamaldehyde. When the animals were previously acclimatizeted, cinnamaldehyde didn´t produce nociceptive behavior. This not occurred with non-acclimatizeted zebrafish (**p< 0.01). Regarding the period, animals were more sensitive to cinnamaldehyde at morning (**p< 0.01) than afternoon (*p< 0.05).
Conclusion: The results suggest that orofacial nociceptive tests should be performed using adult non-acclimatizeted zebrafish on Petri dishes or beakers and in the morning.Background and aims: Adult zebrafish (Danio rerio) has been proposed as a low-cost and simple alternative to the use of higher vertebrates in laboratory research on novel compounds with antinociceptive potential. This study aimed to investigate the orofacial nociceptive response induced by cinnamaldehyde in adult zebrafish, observing environmental changes. 
Methods: Cinnamaldehyde (0.33 µM, 5.0 µL) was applied to the lips of the animals (n=8/group) 30 min after pre-treated (20 µL;i.p) with vehicle (saline) or morphine (5.0 mg/mL). Naive groups (n=8/each) were included. After the applications of the cinnamaldehyde, the animals were transferred to the Petri dishes (10x15cm) or beaker (250mL) and the orofacial nociception was quantified in terms of locomotor activity (0-5min). In another set of experiments, it was evaluated whether acclimatization of animals 24h before the experiments would alter the nociceptive response to cinnamaldehyde. The influence of experiment period (morning or afternoon) was also analyzed. All experimental procedures were approved by the Ethics Committee for the Use of Animals of the State University of Ceará (#7210149/2016). 
Results: The fact that the experiment was carried out on the Petri dish or the beaker did not alter the response to cinnamaldehyde. When the animals were previously acclimatizeted, cinnamaldehyde didn´t produce nociceptive behavior. This not occurred with non-acclimatizeted zebrafish (**p< 0.01). Regarding the period, animals were more sensitive to cinnamaldehyde at morning (**p< 0.01) than afternoon (*p< 0.05).
Conclusion: The results suggest that orofacial nociceptive tests should be performed using adult non-acclimatizeted zebrafish on Petri dishes or beakers and in the morning.

DOES THE ENVIRONMENT INTERFERE WITH THE OROFACIAL NOCICEPTIVE RESPONSE OF THE ADULT ZEBRAFISH?