Neuronal P2X(7) receptors are targeted to presynaptic terminals in the central and peripheral nervous systems

The ionotropic ATP receptor subunits P2X(1-6) receptors play important role s in synaptic transmission, yet the P2X(7) receptor has been reported as ab sent from neurons in the normal adult brain. Here we use RT-PCR to demonstr ate that transcripts for the P2X(7) receptor are present in extracts from t he medulla oblongata, spinal cord, and nodose ganglion. Using in situ hybri dization mRNA encoding, the P2X(7) receptor was detected in numerous neuron s throughout the medulla oblongata and spinal cord. Localizing the P2X(7) r eceptor protein with immunohistochemistry and electron microscopy revealed that it is targeted to presynaptic terminals in the CNS. Anterograde labeli ng of vagal afferent terminals before immunohistochemistry confirmed the pr esence of the receptor in excitatory terminals. Pharmacological activation of the receptor in spinal cord slices by addition of 2 '- and 3 ' -O-(4-ben zoylbenzoyl)adenosine 5 ' -triphosphate (BzATP; 30 muM) resulted in glutama te mediated excitation of recorded neurons, blocked by P2X(7) receptor anta gonists oxidized ATP (100 muM) and Brilliant Blue G (2 muM). At the neuromu scular junction (NMJ) immunohistochemistry revealed that the P2X(7) recepto r was present in motor nerve terminals. Furthermore, motor nerve terminals loaded with the vital dye FM1-43 in isolated NMJ preparations destained aft er application of BzATP (30 muM). This BzATP evoked destaining is blocked b y oxidized ATP (100 muM) and Brilliant Blue G (1 muM). This indicates that activation of the P2X(7) receptor promotes release of vesicular contents fr om presynaptic terminals. Such a widespread distribution and functional rol e suggests that the receptor may be involved in the fundamental regulation of synaptic transmission at the presynaptic site.