Characterization of Ketamine-Induced Neurotoxicity in PND7 Rats as a Model of Pediatric Anesthesia.

Ketamine, a dissociative anesthetic commonly used in pediatric medicine, may induce neurotoxic effects when administered during early neonatal life. Although ketamine-induced neuronal apoptosis has been previously documented, less is known about glial cell responses or temporal evolution of injury. This study investigated the neurotoxic effects of ketamine (20 mg/kg, 5 intraperitoneal injections administered 90 minutes apart) in postnatal day 7 Sprague-Dawley rats of both sexes, compared with age-matched controls. Brains were collected 2 and 16 hours after the last injection and evaluated by histology, immunohistochemistry, and immunofluorescence using markers of apoptosis, DNA damage, and cell populations (Cleaved Caspase-3, γH2AX, NeuN, Iba-1, GFAP, and Olig2). Quantification of apoptotic and immunostained cells in the cortex, hippocampus, and corpus callosum was performed using standardized digital image analysis. Ketamine induced a significant increase in apoptosis and DNA damage at 2 hours, concomitant with an elevation in Olig2-positive cells, suggesting a potential compensatory response. Neuronal, astrocytic, and microglial cells were unaffected. Intrinsic apoptosis primarily involved neurons and oligodendrocytes, with microglia and astrocytes engaged in phagocytosis of apoptotic cells. At 16 hours, a return to baseline levels was observed. These findings offer a temporal and cellular characterization of ketamine-induced neurotoxicity in the developing rat brain.