Corticosterone-linked microglial activity underpins sexually dimorphic neuroplasticity after ketamine anesthesia.

Here, we identify a female-selective corticosterone-mediated microglia-neuron interaction in vivo during ketamine anesthesia recovery, absent in males. This microglia-neuron interaction induces plastic and functional neuronal changes, as evidenced by increased spine density and mEPSC frequency, which is occluded upon microglia depletion.

We show that this process is driven through upregulation of the stress-responsive co-chaperone Fkbp5 mRNA and its protein, FKBP51, in female microglia. Fkbp5/FKBP51 is a key intermediary in a corticosteroid-induced stress response, and its involvement points towards a critical interface between endocrine signaling and microglia. Thus, to counteract the observed KXA-mediated corticosterone increase in the blood, we remove the primary source of corticosterone through adrenalectomy.