Expression of pain receptors in WT and KI neurons. A, Real-time RT-PCR experiments of mRNA extracts from trigeminal ganglia show no significant difference in P2X3 mRNA expression levels between WT and KI mice (n = 3, p > 0.05). Data were normalized with respect to β-tubulin III housekeeping mRNA content. B, Biotinylation experiments of trigeminal neurons in culture show no significant differences in P2X3 membrane protein expression levels between WT and KI mice (n = 4, p > 0.05). C, Real time RT-PCR experiments to measure mRNA expression levels of TRPV1 (left) and P2X2 (right) receptor subunits show no significant difference between trigeminal ganglia from WT and KI mice. n = 3 p > 0.05. Middle panel shows examples of TRPV1 receptor mediated responses evoked by capsaicin (1 μM) from WT or KI neuron, indicating similar amplitude and duration. D, Microphotographs show immunoreactivity of TRPV1 and P2X2 proteins in cultured trigeminal neurons from WT or KI mice. Histograms (right) represent% of immunoreactive neurons for TRPV1 (top) and P2X2 (bottom) over β-tubulin III immunoreactive neurons. n = 5, p > 0.05.