Research Paper Volume 11, Issue 14 pp 5140—5157

Subunit contribution to NMDA receptor hypofunction and redox sensitivity of hippocampal synaptic transmission during aging

Figure 4. NMDAR activity and Ca²⁺ are required for the DTT-induced potentiation of NMDAR synaptic function. (A) Time course of mean (±SEM) NMDAR-fEPSP slope normalized to the baseline (dashed line) for the control condition (open circles), in the presence of ifenprodil or Ro 25-6981 in 2 mM Ca²⁺ recording medium (gray circles), and ifenprodil in 3 mM Ca²⁺ recording medium (filled circles). For clarity, the responses for the GluN2B antagonists (ifenprodil and Ro 25-6981) in 2 mM Ca²⁺ recording medium were combined. The arrow indicates the time of DTT (0.5 mM) application. The insert provides an example of the growth of the NMDAR-mediated fEPSP during baseline (1) and 60 min following application of the DTT (2) under the control condition. (B) Bar graph demonstrates the percent change in NMDAR-mediated fEPSP response during the last 5 min of recording, due to DTT application under the control condition (open bar, n = 31/26 slices/ animals), 2 mM Ca²⁺ + ifenprodil (light gray bar, n = 8/8 slices/animals), 2 mM Ca²⁺ + Ro 25-6981 (gray bar, n = 5/5 slices/animals), and 3 mM Ca²⁺ + ifenprodil (black bar, n = 8/4 slices/animals). (C) Time course of mean (±SEM) NMDAR-fEPSP slope normalized to the baseline (dashed line) for the control condition (open circles), in the presence of NVP in 2 mM Ca²⁺ recording medium (gray circles), and NVP in 3 mM Ca²⁺ recording medium (filled circles). The arrow indicates the time of DTT (0.5 mM) application. (D) Bar graph demonstrates the percent change in NMDAR-mediated fEPSP response during the last 5 min of recording, due to DTT application under the various conditions including control (open bar, n = 31/26 slices/animals), NVP (light gray bar, n = 7/6 slices/animals), and 3 mM Ca²⁺ + NVP (black bar, n= 8/4 slices/animals). For B & D, the asterisks indicate a significant difference relative to control.