Abstract: Objective To explore the effects of hypoxic preconditioning on neurotoxicity induced by propofol in neonatal rats. Methods Seventy‑five 7‑day‑old SPF Sprague‑Dawley rats, weighing 10‒15 g, were divided into five groups (n=15 in each group) using the random number table: a normal saline group (N group), a lipid emulsion group (F group), a propofol group (P group), a hypoxic preconditioning group (H group), and a hypoxic preconditioning+propofol group (H+P group). In the NS group, 100 μl normal saline was injected intraperitoneally; in the F group, 100 μl fat emulsion was injected intraperitoneally; in the P group, 100 mg/kg propofol was injected intraperitoneally; in the H group, rats were placed in 8% oxygen concentration for 10 min, air for 10 min, circulated for 5 times, and recovered in the air for 2 h; rats in the H+P group, received hypoxia pretreatment first (the same as H group) and then propofol was administered intraperitoneally (the same as P group) . At the time of recovery from anesthesia, the rats were sacrificed to collect the hippocampus for the preparation of the specimen. The ultrastructure of hippocampal neurons was observed under a transmission electron microscope. Paraffin sections were adopted for terminal deoxynucleotidyl transferase‑mediated dUTP‑biotin nick end labeling (TUNEL) staining, and the number of positive cells was detected. The expression of cleaved‑caspase‑3, B‑cell lymphoma‑2 (Bcl‑2) and B‑cell lymphoma‑2‑associated X protein (Bax) were determined by Western blot. Results Compared with the N group, the P group presented with shrunk hippocampal neurons, organelle disintegration and disappearance of the nucleoli, with an increased number of TUNEL positive cells (P<0.05), as well as increased expression of cleaved‑caspase‑3 and Bax protein (P<0.05) and decreased expression of Bcl‑2 protein (P<0.05). Compared with the P group, H+P group showed intact cellular membrane of hippocampal neurons, clear organelles and nuclei, and slightly reduced nuclear chromatin, with a decreased number of TUNEL positive cells (P<0.05), as well as declined expression of cleaved‑caspase‑3 and Bax protein (P<0.05) and increased expression of Bcl‑2 protein (P<0.05) Conclusions Hypoxic preconditioning can reduce the neurotoxicity of propofol to the developing brain of rats, which may be partially associated with the up‑regulation of the expression of Bcl‑2 and down‑regulating the expression of Bax and cleaved‑caspase‑3.
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