BACHD mice demonstrate decreases in synaptic activity of medium-sized spiny neurons at 6 months. BACHD mice demonstrate decreases in synaptic activity of medium-sized spiny neurons at 6 months. A, Current-clamp recordings show the voltage deflections induced by hyperpolarizing and depolarizing current pulses in wild-type (WT) and BACHD striatal neurons. At 150 pA, both cells displayed repetitive action potentials. B, Voltage-clamp recordings from the same cells indicated that the overall frequency of spontaneous synaptic currents was not different in cells from WT or BACHD animals. However, medium- and large-amplitude (>20 pA) synaptic currents occurred more frequently in WT cells. C, Graph shows the amplitude–frequency distributions of spontaneous synaptic events. When grouped together, the average number of medium- to large-amplitude synaptic currents was significantly reduced in cells from BACHD mice (p < 0.01, inset). D, Cumulative interevent interval distributions, a measure of release probability, overlapped in cells from WT and BACHD mice. E, In contrast, relative cumulative amplitude distributions revealed that small-amplitude events had higher probability in cells from BACHD compared with cells from WT mice. The asterisks indicate the differences were statistically significant (p < 0.01 to p < 0.001). Error bars indicate SEM. Michelle Gray et al. J. Neurosci. 2008;28:6182-6195 ©2008 by Society for Neuroscience