Swim stress differentially affects limbic contents of 2- arachidonoylglycerol and 2-oleoylglycerol

Restraint stress exposures evoke progressively larger increases in 2-arachidonoylglycerol (2-AG) in limbic brain regions as the number of repetitions increases. The Porsolt swim test usually involves two swim exposures, separated by 24 hours and we asked whether the 2-AG response differed between the first and second exposures. Methods—Four groups of male C57/Bl6N mice were studied: control; exposed to a single 6 minute swim and killed immediately; exposed to a single 6 minute swim and killed 24 hours later; and exposed to 2 swims, separated by 24 hours and killed after the second swim. Outcomes were swim behavior, serum corticosterone, and 2-AG and 2-oleoylglycerol (2-OG) contents in amygdala, hippocampus and prefrontal cortex. Results—Mean 2-AG contents were not significantly different among the four treatment groups in any brain region and did not correlate with immobility in either forced swim exposure. However, 2-AG contents in all three brain regions only of the mice exposed to two swims were significantly, positively correlated with serum corticosterone concentrations measured at the same time. 2-OG is present in brain and exhibits a striking regional heterogeneity in control mice. 2-O