GluR1 subunits can occur as homomers or as heteromers containing GluR2 subunits (Greger et al., 2003). Because GluR1 immunoreactivity rises at synaptic junctions following paired conditioning, a correlative rise of GluR2/3 immunoreactivity might also be expected. In order to test this possibility, we analyzed synapses of the same LA tissue for GluR2/3 immunoreactivity. The analysis indicated that no change was induced by the paired conditioning with regard to the proportion of synapses labeled for GluR2/3 at the synaptic junction of spines (F(2,9) = 0.126, P = 0.88; Fig. 6F), the proportion of spines labeled at nonsynaptic portions (F(2,9) = 0.098; P = 0.91; Fig. 6E), or the proportion of dendritic shaft synapses labeled (F(2,9) = 0.05884, P = 0.94; Fig. 7C). PEG levels at dendritic shaft synapses also were not detectably different (F(2,9) = 0.19031; P = 0.83; Fig. 7D), nor were PEG levels at spine synapses (F(2,9) = 0.32604; P = 0.73).
