Dopamine depletion modulates excitatory synaptic transmission.

<p>(A) Summary histogram of the mean minimal stimulation threshold current required to evoke an EPSP showing a significant increase induced by dopamine depletion. (B) Summary plot of EPSP slope as a function of increasing intensities of stimulation from untreated control and dopamine-depleted MSN. (C) Histogram of the mean slope factor ((mV/ms).mA⁻¹) of the linear part of stimulation-EPSP slope plots in both groups. Dopamine depletion induced an increase in the strength of the excitatory fiber-MSN synapse. (D) Representative stimulation-EPSP slope plots (a) and traces of stimulation-evoked EPSPs recorded in current clamp from untreated control (black in (a) and (b)) and dopamine-depleted (gray in (a) and (c)) MSN. (E) Summary histogram illustrating the intensity of stimulation current needed to evoke an action potential above threshold current to evoke an EPSP. The intensity of current to action potential was significantly decreased in neurons from dopamine-depleted animals which is shown in representative traces from untreated control (Fa) and dopamine-depleted (Fb) MSN. The spike threshold was decreased in dopamine-depleted MSN compared to untreated controls as shown in the representative traces (Fa, Fb) and the values histogram (Fc). (Untreated control medium spiny neurons n = 7, dopamine (DA)-depleted medium spiny neurons n = 7; data represent mean ± SEM; *p<0.05, **p<0.01).