GPR39 and Cognitive impairment: On a cell-specific level, using immunohistochemistry against the third extracellular domain of GPR39-1a in human dorsolateral prefrontal cortex, Davis and colleagues [7] detected protein expression in microglia and peri-capillary cells resembling pericytes, with GPR39-positive microglia increasing in density in brains from deceased individuals with a history of cognitive-impairment.