Although not investigated here, these mechanisms may help explain our current findings because we previously demonstrated in primary cortical neurons and U87MG astrocytoma cells that morphine-induced endolysosome de-acidification, as well as increases in the cytoplasmic protein levels of ferritin heavy chain, were mediated through MORs and Gαi-protein signaling [35]. This evidence concerns the gene FTH1 and astrocytoma (excluding glioblastoma).