EE-rearing for 2 weeks promoted functional and synaptic maturation of dentate granule cells.

<p>(A) Top, response of dentate granule cells from control (left) and EE-reared (right) animals to depolarizing current injections (56 pA, 300 ms). Bottom, granule cell responses to hyperpolarizing current injections (−16 pA, 300 ms). (B) The average input resistance of granule cells from EE-reared mice (1703.3±139.9 MΩ) was significantly lower than that of control mice (2308.4±263.5 MΩ, N = 3 mice each, <i>P</i><0.05). (C) Square wave depolarizing current steps (−16 to 56 pA, 300 ms) were given in 8 pA increments. Quantitation showed that more action potentials were elicited by equivalent current steps in EE-reared mice as compared to controls. (D) Sample mEPSC recordings and average mEPSC waveforms from control and EE-reared mice. (E) EE-rearing did not significantly affect average mEPSC amplitude. (F) EE-rearing significantly increased average mEPSC frequency (Ctrl: 0.53±0.08 Hz; EE: 1.19±0.23 Hz, N = 3 mice each, <i>P</i><0.05), and resulted in a left shift of the cumulative probability distribution (<i>P</i><0.001). (G) Sample mIPSC recordings and average mIPSC waveforms from control and EE-reared mice. (H) The average mIPSC amplitude of EE-reared mice was significantly higher (Ctrl: 14.72±0.78 pA, EE: 18.26±0.94 pA, <i>P</i><0.05), also shown as a right shift of the cumulative probability distribution (<i>P</i><0.01). (I) The average mIPSC frequency of EE-reared mice was significantly increased (Ctrl: 0.92±0.11 Hz, N = 3 mice; EE: 1.84±0.30 Hz, N = 4 mice, <i>P</i><0.01), also shown as a left shift of the cumulative probability distribution (<i>P</i><0.05). Error bars represent s.e.m., and “<i>n</i>”, as indicated inside bar graphs, represents the number of cells recorded; 3–4 mice from age-matched litters were used for each experiment; *<i>P</i><0.05.