Figure 2.

Chemical kinetic schemes of receptors, Ca²⁺ channels, and glutamate transporter. The kinetic rate constants for the reaction pathways are given in Table 1. (A) Glutamate-gated AMPAR with a mixture of GluA1 and GluA2 subunits and (B) glutamate-gated NMDA receptor with a mixture of GluN2A (NR2A) and GluN2B (NR2B) subunits were distributed on the dendritic spine head plasma membrane associated with the PSD. Mg²⁺ block was modeled by the asymmetric trapping block model of Vargas-Caballero and Robinson (2004). (C) Voltage-dependent Ca²⁺ channels on the spine head and neck are the sole source of calcium during backpropagating action potentials. (D) Glutamate transporter representing a combination of GLT-1 and GLAST transporter subtypes were distributed on the astrocytic glial processes.