CCI promotes σ1R-mediated associations of α2δ1-2 proteins with NR1 subunits. (A) CD1 WT sham-operated (n = 4), CD1 WT CCI (n = 4), CD1 σ1R−/− sham (n = 4) and CD1 σ1R−/− CCI (n = 4) were sacrificed 7 days after surgery and PAG synaptosomal fractions were prepared. NR1 subunits were immunoprecipitated (IP) from the solubilized membrane preparations, and the presence of co-precipitated (A) NR1, (B) NR2A, (C) NR2B, (D) α2(δ1), (E) (α2)δ1, and (F) (α2)δ2 proteins was assessed in Western blots (WB). The bars represent the mean ± SD of three measurements. Data are computed relative to the WT mice and in the absence of CCI (assigned the arbitrary value of 1). The arrows refer to the comparison and * indicates significant difference of the CCI group relative to the CD1 WT or CD1 σ1R−/− group: p < 0.05. Details as in Figure 4. (G) CD1 WT mice: effect of S1RA on the association of α2δ1-2 proteins with NR1 subunits promoted by CCI (n = 6). S1RA (3 nM) was injected icv 7 days after CCI surgery in three CD1 WT mice. The animals were sacrificed 30 min later to obtain the synaptosomal fraction from the PAG. The NR1 subunits were immunoprecipitated from the solubilized membrane preparations, and the co-precipitated α2(δ1), α2(δ2), (α2)δ1, and (α2)δ2 were analyzed in Western blots: * indicating significant difference relative to the CCI group, p < 0.05. Sham operated CD1 WT mice (n = 3) served as control to the effect of CCI (for further details see Section 2).