Background & Aims

Orofacial pain is a major public health problem. The prevalence of orofacial pain in the general population rounds between 16.1 and 31%. In Brazil, it is estimated that approximately 10 million people are affected by this condition. Currently, the control of orofacial pain is still difficult to manage. The use of cannabinoid compounds has aroused interest due to their analgesic effects, but there are still gaps in the knowledge about the mechanism of action of the endocannabinoid system (ECS) in orofacial pain. The objective of this study is to investigate the participation of the endocannabinoid agonist WIN 55, 212-2 (WIN) in a model of acute orofacial nociception in adult zebrafish, evaluating its possible antinociceptive and anxiolytic mechanism of action through TRPV1, TRPA1, TRPM8 and NMDA receptors.

Methods

(1) Effect of WIN on the locomotor activity of zebrafish using the open field test. Animals (n = 6/group) received WIN (0.1, 1, 10, or 50 µg/kg, i.p.) or vehicle. A naïve group was included. (2) The animals were pre-treated with WIN (0.1, 1 or 10, µg/kg, 20 ?L, i.p.) or vehicle. A naïve group was included. Orofacial nociception was induced by injection (5.0 ?L) of capsaicin (40.93 ?M), cinnamaldehyde (0.33 ?M), menthol (0.006 %), or glutamate (12.5 ?M) into the zebrafish lips when behavioral analysis was performed. (3) Pretreatment with capsazepine (specific TRPV1 antagonist), HC-030031 (specific TRPA1 antagonist), AMTB (TRPM8 antagonist) or Ketamine (NMDA antagonist) were used 30 min before WIN (0.1 µg/mL), when behavioral analysis was performed. (4) The animals received WIN (0.1, 1 or 10 µg/kg, 20 ?L, i.p.) or vehicle, 30 min before the anxiolytic effect be quantified by the time spent in the clear zone of a glass tank containing water (5 min).

Results

WIN did not change the locomotor activity compared to the control and the naïve groups. WIN 0.1 µg/mL (p<0.001) and 1 µg/mL (p<0.03) reduced the orofacial nociceptive effect induced by capsaicin (40.93 ?M). WIN 0.1 µg/mL (p<0.0004) and 1 µg/mL (p<0.01) reduced the orofacial nociceptive effect induced by cinnamaldehyde (0.33 ?M). WIN 0.1 µg/mL (p<0.001) reduced the orofacial nociceptive effect induced by menthol (0.006 %). WIN 0.1 (p<0.001), 1 (p<0.03) and 10 µg/mL (p<0.04) reduced the orofacial nociceptive effect induced by glutamate (12.5 ?M). The previous application of capsazepine (specific TRPV1 antagonist), but not HC-030031 (specific TRPA1 antagonist), AMTB (TRPM8 antagonist) or Ketamine (NMDA antagonist) was able to inhibit the antinociceptive action of WIN. Also, WIN (0.1 and 1 µg/mL) increased the time spent in the clear zone compared to the control and naive groups.

Conclusions

This result suggests that WIN 55, 212-2 exerts orofacial antinocieptive effect through TRPV1 receptors. Beyond this, WIN 55, 212-2 did not alter the locomotor activity of the zebrafish and developed anxiolytic effect.

References

HORST, O. V et al. Prevalence of pain in the orofacial regions in patients visiting general dentists in the Northwest Practice-based REsearch Collaborative in Evidence-based DENTistry research network. Journal of the American Dental Association (1939), v. 146, n. 10, p. 721– 8.e3, out. 2015.
MAGALHÃES, F. E. A. et al. Adult Zebrafish (Danio rerio): An Alternative Behavioral Model of Formalin-Induced Nociception. Zebrafish, v. 14, n. 5, p. 422–429, 1 out. 2017.
SOARES, I. C. R. et al. Oleanolic acid promotes orofacial antinociception in adult zebrafish (Danio rerio) through TRPV1 receptors. Chemico-Biological Interactions, v. 299, p. 37–43, 1 fev. 2019.
SAMPAIO, G. M. M. S. et al. Melatonin promotes orofacial antinociception in adult zebrafish by modulating TRP channels. Physiology & Behavior, v. 269, p. 114238, 1 out. 2023.

Presenting Author

Hellíada Vasconcelos Chaves

Poster Authors

Hellíada Chaves

Professor

Federal University of Ceará

Lead Author

Joanna Trycia Magalhães Alexandre-Lima

Graduate Program in Dentistry, Federal University of Ceará

Lead Author

Erlânia Alves de Siqueira

Federal University of Ceará

Lead Author

Sacha Aubrey Alves Rodrigues Santos

University of Fortaleza

Lead Author

Ana Lívia Oliveira de Sousa Rodrigues

RENORBIO, University of Fortaleza

Lead Author

Mirna Marques Bezerra

Federal University of Ceará

Lead Author

Adriana Barros

University of Fortaleza

Lead Author

Topics

  • Treatment/Management: Cannabinoids and Cannabis