Blockade of Adrenal Medulla-Derived Epinephrine Potentiates Bee Venom-Induced Antinociception in the Mouse Formalin Test: Involvement of Peripheral β-Adrenoceptors
Figure 5
Graphs illustrating the antinociceptive effect of DBV administered together with adrenoceptor antagonists on formalin-induced pain responses during the early and late phases of the formalin test. (a) Injection of DBV (Veh + DBV + F) decreased pain responses compared to the vehicle-injected group (Veh + Veh + F, **). Coadministration of phentolamine with DBV or vehicle [Phento (5, 10 mg) + DBV + F, Phento (5, 10 mg) + Veh + F] did not change formalin-induced pain behaviors as compared to each control group during either the early or late phase. (b) The group receiving vehicle plus DBV and formalin (Veh + DBV + F) showed suppressed pain responses compared to the vehicle- plus-vehicle and formalin-injected group (Veh + Veh + F, **). Injection of propranolol and nadolol with vehicle [PRO (5 mg) + Veh + F, Nadolol (20 mg) + Veh + F] did not change formalin-induced pain responses as compared to the DBV-treated group during the early or late phase. Propranolol and nadolol with DBV treatment [PRO (5 mg) + DBV + F, Nadolol (20 mg) + DBV + F] significantly suppressed formalin-induced pain during the late phase (# and ## as compared with DBV-treated group) but not during the early phase.
