Nociceptive stimulation activates NR2B-mediated DISC1/GSK-3β and ERK/CREB signaling alleviates sevoflurane induced neurotoxicity in neonatal rats.

BACKGROUND

Sevoflurane (SEVO) has been extensively confirmed to induce neurotoxicity in the neonatal brain, but the existing studies were conducted in healthy subjects without harmful stimulation, which is inconsistent with the conditions for the clinical application of SEVO. This study attempted to explore the effects of preoperative pain on sevoflurane induced neurotoxicity and related mechanisms.

METHODS

Postnatal day 7 (P7) Sprague-Dawley (SD) rat pups were exposed to 2.5% SEVO for 1.5 h, 3 h, 4.5 h, 6 h, respectively. Another group of rats were exposed to 2.5% SEVO for 6 h after receiving once injection of 10 μL Complete Freund's Adjuvant suspension (CFA, diluted with saline at a ratio of 1:9) into the both hind paws to induce acute pain. Furthermore, a third group of pups were once intraperitoneally injected with lithium chloride (Li, 120 mg/kg), followed by 2.5% SEVO exposure for 6 h. Western blot was used to determine the levels of NR2B, DISC1, GSK-3β, SYP, PSD95, ERK and CREB proteins in the developing brain. Neuroapoptosis was detected by TUNEL assay and immunostaining of cleaved-caspase-3.

RESULTS

SEVO time-dependently downregulated the levels of NR2B, DISC1, SYP, PSD95, pGSK-3β/GSK-3β, pCREB/CREB, and pERK/ERK, and increased cleaved-caspase-3 expression and the number of TUNEL-positive cells in the neonatal brain. CFA treatment alleviated SEVO-induced neuroapoptosis and increased the expression levels of NR2B, DISC1, SYP, PSD95, pGSK-3β/GSK-3β, pCREB/CREB, and pERK/ERK in the neonatal brain. Notably, co-treatment with Li mitigated SEVO-induced neurotoxic changes as well.

CONCLUSIONS

SEVO exposure during infancy induces neuroapoptosis and impairs synaptic development. Preoperative pain attenuates SEVO-induced neurodevelopmental impairments by promoting NR2B expression, which activates DISC1/GSK-3β and ERK/CREB signaling pathways.