Figure 7
From: Facilitation of neocortical presynaptic terminal development by NMDA receptor activation
Models of presynaptic terminal development by activation of NMDARs. NMDAR activation by glutamate could regulate presynaptic development via at least four mechanisms: (1) glutamate released from presynaptic terminals could activate postsynaptic NMDARs, then postsynaptic neurons could release a retrograde signal that controls presynaptic development; (2) activation of postsynaptic NMDARs could induce transmission of a transneuronal signal, regulating presynaptic development in the activated neuron; (3) glutamate released from presynaptic terminals could activate presynaptic autoreceptors to cell-autonomously regulate presynaptic development; (4) glia could release glutamate to activate NMDARs and regulate presynaptic development. Mechanisms 1 and 2 are mediated by activation of postsynaptic NMDARs, while mechanisms 3 and 4 are mediated by presynaptic NMDARs. The data presented here are most consistent with mechanisms 2 and 3 since NMDAR activation controlled presynaptic protein accumulation in the absence of glia and at synapses that lacked postsynaptic NMDARs.