Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Background Temporomandibular joint (TMJ) receives rich sympathetic innervations that may contribute to TMJ pain through the local release of sympathomimetic amines. The aim of this study was to determine whether blockade of beta-adrenoceptors in the TMJ of male and female rats reduces formalin-induced TMJ nociceptive behaviour. Methods We co-administrated each one of the selective beta 1-, beta 2- and beta 3-adrenoceptors antagonists, atenolol, ICI 118.551 and SR59230A, respectively, with formalin in the TMJ of male and proestrus and dioestrus female rats. Because intra-temporomandibular joint formalin induces significantly different concentration-dependent responses among the three groups, with dioestrus females showing greater responses than males or proestrus females, equi-nociceptive formalin concentrations were used to test the effects of the beta-adrenoceptor antagonists. Results We found that atenolol, ICI 118.551 and SR59230A significantly reduced formalin-induced TMJ nociception in a dose response fashion in both males and females. However, a lower dose of each beta-adrenoceptor antagonist was sufficient to significantly reduce nociceptive responses in females than in males. Administration of the highest doses of each beta-adrenoceptor antagonist in the TMJ contralateral to that receiving formalin did not affect formalin-induced nociception in males and females, confirming the local action of the beta-adrenoceptor antagonists. Conclusions We conclude that blockade of beta-adrenoceptors in the temporomandibular joint suppresses formalin-induced TMJ nociceptive behaviour in both males and females but females are more responsive. These findings suggest that the use of beta-blockers in the treatment of TMJ pain might be of benefit, especially in females.16913021310Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)