Background: The anesthetic isoflurane can cause neurotoxicity in fetuses and offspring of rats, affecting their neurodevelopment. However, the underlying mechanisms and therapeutic targets of isoflurane-induced neurotoxicity remain to be identified. Alfaxalone (ALF) is a steroid anesthetic. Steroids have been reported to have neuroprotective effects. This study aimed to investigate whether ALF could alleviate the isoflurane-induced neurotoxicity in fetuses and offspring of rats.

Methods: On gestation day 15 (G15), the pregnant SD rats were randomly assigned to 4 groups: control 1 (CTL1) + control 2 (CTL2), isoflurane (ISO) + CTL2, CTL1 + ALF, and ISO + ALF. To analyze the changes in the expression levels of inflammatory cytokines, apoptotic factors, and synaptophysin, the brain tissues from the G15 fetuses and offspring at postnatal day 7 (P7), postnatal day 14 (P14), and postnatal day 31 (P31) were collected. The newborn neurons in the rats’ offspring at P7, P14, and P31 were counted using immunofluorescence techniques. The Morris water maze (MWM) test was performed to assess the learning and memory abilities of P31 offspring rats.

Results: ALF significantly alleviated the isoflurane-induced increase in the expression levels of inflammatory cytokines and apoptotic factors, such as interleukin (IL)-6 (ISO + CTL2 versus ISO + ALF: 5.133 ± 0.739 versus 1.093 ± 0.213, P < .001) and Caspase-3 (6.457 ± 0.6 versus 1.062 ± 0.1, P < .001) in the G15 fetuses. In P31 offspring rats, the expression levels of synaptophysin (0.719 ± 0.04 versus 1.068 ± 0.072, P < .001) and the number of newborn neurons in the dentate gyrus of the hippocampus were significantly lower in the ISO + CTL2 group as compared to those in the ISO + ALF group (118 ± 6 versus 140 ± 7, P < .001). These changes also occurred in the rat offspring at P7 and P14. In the MWM test, the escape latency of CTL1 + ALF group rats was significantly lower than that of ISO + ALF group rats (41 ± 6 versus 31 ± 7, P < .001) at P31.

Conclusions: Based on these findings, this study suggested that isoflurane exposure during pregnancy in rats could cause neuroinflammation and death of embryos as well as impairment of cognitive function in the offspring rats. ALF can be used to counteract the negative effects of isoflurane.

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Xingkai Zhao et al.
Anesthesia & Analgesia March 2023