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. 2016 Aug 4;6:30743. doi: 10.1038/srep30743

Figure 6. Increased amount of membrane GluN2B enhances intrinsic excitability of CA1 neurons in response to somatic depolarization after fear conditioning.

Figure 6

(A,B) The number of action potential in CA1 neurons was increased after fear conditioning. (A) Representative sweeps of action potentials (APs) elicited by a 100-pA depolarization current in a CA1 pyramidal neuron from rat unconditioned (black) versus conditioned with single (blue) or 5 CS-US (red). RMP, resting membrane potential. Arrows indicate a hyperpolarization current to monitor input resistance (Rin). Calibration: 30 mV, 200 ms. (B) Averaged AP number elicited by a sequence of depolarization pulses ranging from 0–200 pA. *p < 0.05 for 5 CS-US vs. context control, #p < 0.05 for 1 CS-US vs. context-control, and &p < 0.05 for 1 CS-US vs. 5 CS-US. (C,D) (C) Detail of the first action potential fired by the examples in (A). The arrows are the point where after-hyperpolarization (AHP) measurements were made (20–50 ms after each action potential). The black trace corresponds to the control neuron; the blue trace, to a single CS-US conditioned neuron; and the red trace, to a five CS-US conditioned neuron; (D) Summary of the medium AHP (mAHP) voltage for each of the first 4 APs in unconditioned and conditioned neurons, using the same data set as in B. *p < 0.05, **p < 0.01. (E–G) Resting membrane potential (RMP) (E), input resistance (Rin) (F), and current-voltage relationship curves (G) were not affected by fear conditioning, using the same data set as in B. (H–J) Blockade of GluN2B decreased the number of APs. (H) Examples of responses to a 160-pA depolarization current pulses (bottom) before (BL) and during the application of ifenprodil (Ifen) in pyramidal neurons of CA1 slices taken from context-control rats (black) versus rats conditioned with single (blue) or 5 CS-US (red). Calibrations: 30 mV, 200 ms. (I) Change in AP number before (BL) and during ifenprodil (Ifen) application. Data obtained from the same neuron are linked by lines. *p < 0.05, **p < 0.01, paired t-test. (J) Summary of the effect of ifenprodil on AP number. **p < 0.01.