We have also evaluated levels of the 2-AG precursors, OAG, and SAG, after acute and repeated restraint stress. OAG and SAG are likely the predominant DAG species present in neuronal cells, and are depleted by DAGL∝ over expression (Jung et al, 2007), suggesting they serve as precursors for 2-AG synthesis. Our data indicate that both DAGs are elevated by repeated, but not acute, restraint stress. As SAG appeared to increase progressively throughout the 60 min stress exposure, we suggest that increases in DAGs are triggered by exposure to the 10th restraint episode, rather than an enduring effect initiated by earlier restraint sessions. The increase in OAG is ~2–3 pmol/mg, whereas the increase in SAG is ~30 pmol/mg. The increase in 2-AG is ~5 pmol/mg, suggesting that increased substrate availability could contribute to the transient increase in 2-AG observed in the same region. The source of increased DAGs is unknown but may be related to increased phospholipase-C activity initiated by upstream Gq-coupled receptor activation.
