P2X 3 , but not P2X 1 , receptors mediate ATP-activated current in neurons innervating tooth-pulp

Summary We developed a method that allows us to label nociceptive neurons innervating tooth-pulp in rat trigeminal ganglion neurons using a retrograde fluorescence-tracing method, to record ATP-activated current in freshly isolated fluorescence-labeled neurons and to conduct single cell immunohistochemical staining for P2X 1 and P2X 3 subunits in the same neuron. Three types of ATP-activated current in these neurons (F, I and S) were recorded. The cells exhibiting the type F current mainly showed positive staining for P2X 3 , but negative staining for P2X 1 . The results provide direct and convincing evidence at the level of single native nociceptive neurons for correlation of the characteristics of ATP-activated currents with their composition of P2X 1 and P2X 3 subunits and cell size. The results also suggest that the P2X 3 , but not P2X 1 , is the main subunit that mediates the fast ATP-activated current in nociceptive neurons.