Blockade of Cannabinoid CB1 Receptors in the Dorsal Periaqueductal Gray Unmasks the Antinociceptive Effect of Local Injections of Anandamide in Mice

Autor(es)

Mascarenhas, Diego C. ^{[1, 2, 3]} ; Gomes, Karina S. ^[1] ; Sorregotti, Tatiani ^{[1, 2, 3]} ; Nunes-de-Souza, Ricardo L. ^{[1, 2, 3]}

Afiliação do(s) autor(es)

^[1] Sao Paulo State Univ, Sch Pharmaceut Sci, Lab Neuropsychopharmacol, Araraquara, SP - Brazil

^[2] Univ Fed Sao Carlos, Joint Grad Program Physiol Sci, Sao Carlos, SP - Brazil

^[3] Sao Paulo State Univ, Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: FRONTIERS IN PHARMACOLOGY; v. 8, OCT 4 2017.
• Citações Web of Science: 0

Resumo

Divergent results in pain management account for the growing number of studies aiming at elucidating the pharmacology of the endocannabinoid/endovanilloid anandamide (AEA) within several pain-related brain structures. For instance, the stimulation of both Transient Receptor Potential Vanilloid type 1 (TRPV1) and Cannabinoid type 1 (CB1) receptors led to paradoxical effects on nociception. Here, we attempted to propose a clear and reproducible methodology to achieve the antinociceptive effect of exogenous AEA within the dorsal periaqueductal gray (dPAG) of mice exposed to the tail-flick test. Accordingly, male Swiss mice received intra-dPAG injection of AEA (CB1/TRPV1 agonist), capsaicin (TRPV1 agonist), WIN (CB1 agonist), AM251 (CB1 antagonist), and 6-iodonordihydrocapsaicin (6-IODO) (TRPV1 selective antagonist) and their nociceptive response was assessed with the tail-flick test. In order to assess AEA effects on nociception specifically at vanilloid or cannabinoid (CB) substrates into the dPAG, mice underwent an intrinsically inactive dose of AM251 or 6-IODO followed by local AEA injections and were subjected to the same test. While intra-dPAG AEA did not change acute pain, local injections of capsaicin or WIN induced a marked TRPV1-and CB1-dependent antinociceptive effect, respectively. Regarding the role of AEA specifically at CB/vanilloid substrates, while the blockade of TRPV1 did not change the lack of effects of intra-dPAG AEA on nociception, local pre-treatment of AM251, a CB1 antagonist, led to a clear AEA-induced antinociception. It seems that the exogenous AEA-induced antinociception is unmasked when it selectively binds to vanilloid substrates, which might be useful to address acute pain in basic and perhaps clinical trials. (AU)

• Processo FAPESP: 13/01283-6 - Sistema hierárquico de defesa no camundongo: modulação pelo fator de liberação de corticotrofina (CRF)
• Beneficiário: Ricardo Luiz Nunes de Souza
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 13/06764-2 - A antinocicepção induzida pela derrota social: implicações da neurotransmissão vaniloide espinal e supraespinal em camundongos.
• Beneficiário: Diego Cardozo Mascarenhas
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 13/03445-3 - Efeitos da superexpressão do Fator de Liberação de Corticotropina (CRF) e nocaute de receptores Crf1 e Crf2 em regiões límbicas sobre o comportamento defensivo de camundongos: influência do estresse agudo e crônico
• Beneficiário: Karina Santos Gomes
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado