Figure 4. Decrease of arc mRNA level after PPS fails to occur when NMDA receptors are blocked.

A1) Means ± s.e.m.s of the amplitude of the population spike, expressed as a percent of baseline, evoked by commissural stimulation before and after PPS (wide down-ward arrow) recorded from animals decapitated 20 min after PPS delivered in either the presence of D-APV (gray circles, n=9) or the absence of drug (black squares, n=7). The data from the latter group were shown in Fig. 3. A1 and are included here for purposes of comparison. Inserts above show representative waveforms (average of 10 recordings) recorded 5 min before (stippled line) and 17 min after PPS (solid line) from an animal that received PPS in the presence of D-APV. Scale: 2 mV, 2 ms. A2) Means ± s.e.m.s of arc mRNA level in dorsal area CA1 (experimental), relative to ventral area CA1 (control), detected in tissue samples harvested 20 min after PPS delivered in either the presence of D-APV (D-APV + PPS, gray bar) or the absence of drug (PPS only, black bar). The data from the latter group were shown in Fig. 3. B and are included here for purposes of comparison. Arc expression levels were normalized by gapdh expression in the respective tissue samples and, to approximate a normal distribution of the data, log₂ -transformed. Fold differences (FD) can be calculated from log₂(RQ) by the formula FD= 2^log2(RQ). Determined Ct values for the two groups are shown in Table 1 in the Supplementary Information. Two-tailed t-tests indicate that the significant decrease of arc mRNA level 20 min after PPS in the absence of drug is abolished in the presence of D-APV. B1) Means ± s.e.m.s of the amplitude of the population spike, expressed as a percent of baseline, evoked by commissural stimulation before and after PPS (wide down-ward arrow) recorded from animals decapitated 70 min after PPS delivered in the presence of either ActD (gray circles, n=6) or vehicle solution (black squares, n=6). Insert above shows representative waveforms (average of 10 recordings) recorded 5 min before (stippled line) and 70 min after PPS (solid line) from an animal that received PPS in the presence of ActD. Scale: 2 mV, 2 ms. B2) Means ± s.e.m.s of arc mRNA level in dorsal area CA1 (experimental), relative to ventral area CA1 (control), detected in tissue samples harvested 70 min after PPS delivered in the presence of either ActD (ActD + PPS, gray bar) or vehicle solution (veh + PPS, black bar). Arc expression levels were normalized by gapdh expression in the respective tissue samples and, to approximate a normal distribution of the data, log₂ -transformed. Fold differences (FD) can be calculated from log₂(RQ) by the formula FD= 2^log2(RQ). Determined Ct values for the two groups are shown in Table 1 in the Supplementary Information. A two-tailed t-test indicates a significant increase in arc mRNA level 70 min after PPS in the presence of vehicle solution (** p < 0.01). This effect was abolished completely in the presence of ActD; in fact, a two-tailed t-test indicates a small but significant decrease in arc mRNA level 70 min after PPS in the presence of ActD (* p < 0.05).