Figure 2.

The physiological properties of MSO principal neurons undergo developmental changes after hearing onset. A, Synaptically evoked EPSPs(4–6 mV) with normalized amplitudes at P14, P23, and P36 show that EPSP shape is developmentally regulated. Strychnine (1 μm) blocked glycinergic inhibition during all cases of synaptic stimulation. B, The rate of rise for EPSPs remained relatively stable after hearing onset (n = 67). C, In the same neurons as in B, the duration of EPSPs, measured at half-maximal amplitude, declined nearly one-third between P14 and P21 with a single exponential time constant of 4.3 d. D, The input resistance (left axis; circles) and membrane time constant (right axis; triangles) of 68 principal neurons declined threefold over the same time window, both with time constants of 3.3 d (single exponential fit). The fits for input resistance (black) and membrane time constant (gray) essentially overlap.