Figure 1.
NMDAR contributes to MSN depolarization during UP states. A, Diagram illustrating the position of microdialysis probes (DP) and sharp microelectrodes (SE). Cx, Cerebral cortex; St, striatum. B, Microphotograph showing the location of the probe and MSN (arrowhead) in a representative experiment. Inset, MSN at higher magnification. C, Averages of >50 UP state (left) and DOWN state (right) onsets recorded from a MSN in baseline conditions (thin lines), after 15 min of AP-5 100 μm infusion (black lines), and 40 min after discontinuing AP-5 (dashed lines). To allow comparing the slope of the waveforms, those corresponding to AP-5 were also scaled to the baseline maximum (gray lines). The time axis was inverted for transitions to the DOWN state, to allow assessing putative hysteretic effects of AP-5 (Wolf et al., 2005). Note that AP-5 reduced UP state amplitude without changing UP state slopes. D, Effect of AP-5 on UP state amplitude (left). AP-5 was infused at 100 μm in seven and at 200 μm in two rats (filled squares). Right, Lack of change of UP state amplitude in eight MSNs recorded under continuous aCSF (circles) and nine MSNs recorded in naive rats (crosses). *p < 0.001 versus baseline, Tukey test after p < 0.006 interaction in a two-way ANOVA with MSN group and treatment (repeated measure) as factors. E, Simultaneous cortical LFP and intracellular recording in one rat treated with AP-5 100 μm. Spontaneous firing ceased during AP-5 administration. F, Expanded view (500 ms after transition) of three consecutive UP states in the baseline condition and under AP-5 in another MSN. G, Frequency dependent effect of AP-5 on membrane potential during UP states. *p < 0.001 versus baseline, Tukey's test after p = 0.003 interaction in a two-way ANOVA. For technical details, see supplemental material (available at www.jneurosci.org).