Figure 7.

Effects of elevation of [Mg²⁺]_o in vitro on synaptic NMDAR current and synaptic plasticity in the infralimbic prefrontal cortex and lateral amygdala. A, Left, Representative traces of AMPA receptor EPSC (gray trace) and NMDAR EPSC (black traces) recorded at membrane potentials of −60 and +50 mV, respectively, in the infralimbic prefrontal cortex. Right, The ratio of amplitude of NMDAR EPSCs to amplitude of AMPA receptors EPSCs (I_NMDA/AMPA) calculated for each cell in the infralimbic prefrontal cortex slices incubated (5 h) under physiological extracellular magnesium concentration (0.8-[Mg²⁺]_o, n = 7) and elevated [Mg²⁺]_o (1.2-[Mg²⁺]_o, n = 7). Elevation of [Mg²⁺]_o in vitro significantly increased the I_NMDA/AMPA in the infralimbic prefrontal cortex. B, Left, Long-term potentiation (as percentage of baseline) induced by the spike timing protocol (arrow) in the infralimbic prefrontal cortex slices (0.8-[Mg²⁺]_o slices, n = 6; 1.2-[Mg²⁺]_o slices, n = 9). Insets, Representative traces of EPSC are presented before (solid line) and after (dotted line) induction of long-term potentiation. Right, The magnitude of long-term potentiation (average over last 5 min) of 0.8-[Mg²⁺]_o and 1.2-[Mg²⁺]_o slices. Elevation of [Mg²⁺]_o in vitro significantly increased the long-term potentiation in the infralimbic prefrontal cortex. C, Same as A, but in the lateral amygdala (0.8-[Mg²⁺]_o, n = 7; 1.2-[Mg²⁺]_o, n = 8). D, Same as B, but in the lateral amygdala (0.8-[Mg²⁺]_o, n = 6; 1.2-[Mg²⁺]_o, n = 5). Elevation of [Mg²⁺]_o in vitro did not significantly change the I_NMDA/AMPA ratio or long-term potentiation in the lateral amygdala. Dashed lines indicate the normalized basal synaptic responses. *p < 0.05. Data presented as mean ± SEM.