Injecting (2R,6R)-hydroxynorketamine ((2R,6R)-HNK) into the brain's lateral ventricle of rats with PTSD-like behaviors most effectively reduces anxiety and fear when given during the reconsolidation phase of fear memory—the period after a memory is recalled and before it is stored again. The drug restored levels of three proteins in the hippocampus (GluA1, VGF, and BDNF) that were lowered by stress and fear conditioning. No significant improvements occurred when the drug was given during the acquisition or extinction phases. The findings suggest that (2R,6R)-HNK works through the VGF/BDNF/GluA1 signaling pathway in the hippocampus to alleviate PTSD-like symptoms specifically during memory reconsolidation.
In rats exposed to a combined stress model (single prolonged stress plus plantar shock), those treated with (2R,6R)-hydroxyketamine (HNK) showed reduced depression- and anxiety-like behaviors, including increased exploratory activity. The compound reversed stress-induced disruptions in the PI3K/AKT signaling pathway in the hippocampus and prefrontal cortex, but not in the amygdala. Traumatic stress itself altered PI3K/AKT signaling in all three brain regions. These results suggest that (2R,6R)-HNK may alleviate negative emotional symptoms after trauma by modulating PI3K/AKT signaling, particularly in the hippocampus.