mRNA expression levels were evaluated in the amygdaloid complex (focused on the lateral, accessory basal and basal nuclei) of the Study I multi-drug population that consisted of subjects with heroin, cocaine or polysubstance heroin-cocaine use as well as normal controls (Table 1). No significant group differences were detected in the mRNA expression levels of GluA1, PSD-95 or Homer 1 in the amygdala subregions studied (Fig. 1, Table 3). However, a very strong positive correlation was observed between GluA1 and PSD-95 in the drug users that was absent in control subjects (Table 4). Although the pattern was consistent throughout the amygdala subnuclei, all substance abuse groups showed the most significant alterations in the lateral nucleus. For example, the correlation between GluA1 and PSD-95 in the lateral amygdala for heroin subjects was r=0.95 (p=0.01), cocaine r=0.94 (p=0.005) and heroin-cocaine r=0.94 (p=0.002; (Figure S1 in Supplement 1). However, no significant positive correlation was observed between GluA1 and PSD-95 in the control group in any subnuclei (e.g., lateral nucleus, r=0.60, p=0.20; Figure S1A in Supplement 1) and even a negative trend was observed in the basal nucleus (r= −0.74, p=0.09).
