Figure 5.
In vivo Epac mediates epinephrine-induced hyperalgesia via PI-PLC, PLD, and PKCϵ. A, Injection of epinephrine (0.1 μg in 2.5 μl) and CTPOMe (6.3 μg in 2.5 μl) produce hyperalgesia of similar magnitude, whereas saline vehicle injection has no effect. CPTOMe-induced sensitization can be completely blocked by the preinjection of the specific PKCϵ inhibitory peptideϵV1-2 (1 μg in 2.5 μl) 30 min before stimulation with CPTOMe, demonstrating that, in vivo, Epac also induces mechanical hyperalgesia through activation of PKCϵ. B, Epinephrine-induced (filled bars) and CPTOMe-induced (dotted bars) mechanical hyperalgesia can be completely blocked by preinjection of the PI-PLC inhibitor U73122 (2.5 μl, 1 μg/μl), but not its inactive control, U73343 (2.5 μl, 1 μg/μl), 30 min before epinephrine/CPTOMe stimulation. Likewise, resembling our in vitro data, the injection of the PLD inhibitor 1-butanol (2.5 μl, 10.9 m), but not its inactive control, 2-butanol, completely inhibits the sensitization through epinephrine/CPTOMe injection. The inhibitors show little or no effect on saline control injections (open bars). Both phospholipases are therefore also necessary for the mediation of β2-AR-stimulated/Epac/PKCϵ-mediated mechanical hyperalgesia in vivo. **p < 0.01. Error bars represent SEM.