Figure 4.

P2X₂-GFP hot spots. (A) Representative examples of dendrites expressing K69A P2X₂-GFP receptors. ATP had no effect compared with the control. (B) Representative examples of dendrites expressing T18A P2X₂-GFP receptors. ATP had no effect compared with control. (C) (Left) 2.5s 100 μM ATP application did not evoke any membrane currents from this representative hippocampal neuron expressing K69A P2X₂-GFP receptors. The cells were healthy because glutamatergic excitatory postsynaptic currents were observed (downward deflections). (Center) 2.5 s 100 μM ATP-evoked currents (5 min apart) from a single hippocampal neuron expressing P2X₂-GFP receptors. The second response was larger than the first (see Fig. 5 for further experiments), and there was <10% desensitization. (Right) 2.5-s 100 μM ATP-evoked currents (5 min apart) from a single hippocampal neuron expressing T18A P2X₂-GFP receptors. Note that the second response is smaller than the first (see also Fig. 5). The traces in Center and Right are normalized to the peak of the first response.