We have demonstrated that the activation of
P2X3 receptor on peripheral afferent neurons is critical to development of inflammatory
hyperalgesia in peripheral tissue, although pharmacological administration of
prostaglandin E(2) or
sympathomimetic amines is enough to sensitize primary afferent neurons by acting directly in neuronal receptors. Therefore, to clarify this ambiguity this study verifies whether
P2X3 receptor activation on primary afferent neurons enables the sensitization induced by
prostaglandin E(2) or
sympathomimetic amine. Initially, this study confirmed that co-administration of
A317491 (60 μg/paw), a selective
P2X3 receptor antagonist, or pre-treatment with
dexamethasone (1 mg/mL/kg) prevents the
mechanical hyperalgesia induced by
carrageenan (300 μg/paw) in the rat's hind paw. Sub-threshold doses of
PGE(2) (4 ng/paw) or
dopamine (0.4 μg/paw), that do not induce
hyperalgesia by themselves, when injected just following αβmeATP or
carrageenan in rats treated with
dexamethasone induced
hyperalgesia, which is prevented by
A317491 or treatment with periganglionar (DRG-L5)
injections of ODN-antisense, against
P2X3 receptor. Furthermore, because PKCɛ translocation induces an increase of neuronal susceptibility to inflammatory mediators, this study demonstrates that αβmeATP in peripheral tissue increases the expression of PKCɛ in cell membranes of DRG-L5, and in contrast, the administration of PKCɛ translocation inhibitor (1 μg/paw) in peripheral tissue 45 min before αβmeATP, prevented the
hyperalgesia induced by sub-threshold dose of
PGE(2) (4 ng/paw). In conclusion, this study suggests that neuronal
P2X3 receptor activation and the consequent PKCɛ translocation increase the susceptibility of nociceptor to inflammatory mediators allowing the development of inflammatory
hyperalgesia.