Figure 9.

Glutamate receptor subunit localization relative to the PSD, defined by PSD95 staining, is altered after incubation of craving. Additional analysis of array tomography data was performed to estimate centrality versus laterality of glutamate receptor subunit expression in the PSD, focusing on spine heads exhibiting punctae positive for both PSD95 and GluA1 (77 and 80 for saline and cocaine groups, respectively), PSD95 and GluN3A (52 and 41), or PSD95 and GluN3B (31 and 51). Bar graphs represent the average percent of GluA1, GluN3A, or GluN3B punctae that spatially overlapped >50% (central expression) or <50% (lateral expression) with PSD95 punctae. First, for each subunit in each experimental group, the balance of expression between central and lateral compartments was compared using paired t tests: saline GluA1, t₍₁₀₎ = −3.97, p = 0.003; saline GluN3A, t₍₉₎ = −0.217, p = 0.83; saline GluN3B, t₍₉₎ = 0.383, p = 0.71; cocaine GluA1, t₍₉₎ = −2.47, p = 0.04; cocaine GluN3A, t₍₉₎ = −0.93, p = 0.38; cocaine GluN3B, t₍₉₎ = 4.86, p = 0.002 (*p < 0.05). We also compared the percent lateral expression for each subunit between saline and cocaine groups using one-way ANOVA: GluA1, F_(1,17) = 18.3, p = 0.0005; GluN3A, F_(1,16) = 0.35, p = 0.56; GluN3B, F_(1,15) = 5.76, p = 0.03 (*p < 0.05). Because these data are expressed as percent control, central locations are the inverse of lateral locations, so where there was a significant increase in laterality, there was also a significant reduction in centrality. For clarity, only significant changes in laterality are indicated by lines/asterisks in the figure.