Methodology for the Study of Learning and Memory in Juvenile Rats Using Sevoflurane Anesthesia to Assess Hippocampal p-CREB and c-fos Expression

Studying cognitive impairments during brain development faces challenges due to the dynamic nature of neurodevelopment, methodological constraints, and contextual barriers. This study investigated an integrated methodological approach to study cognitive impairments in the developing brain caused by sevoflurane based on memory and p-CREB and c-fos expression in hippocampal neurons through the NMDAR/p-CREB/c-fos signaling pathway in juvenile rats. Sixty-four 21-day-old SD male rats (body weight <80 g) were divided into five groups: normal (n=8), 60% O2 (n=16), sham training (n=8), single-dose sevoflurane (n=16), and multiple-dose sevoflurane (n=16). The two sevoflurane groups were sub-grouped into sacrifice 1 day (groups sev1a and sev1b) and 30 days (groups sev30a and sev30b) after training (n=8/subgroup); all other rats were sacrificed 1 h after training. The Y-maze test was used to evaluate learning and memory retention. Immunohistochemistry was used to determine the number of p-CREB- and c-fos-positive neurons in the hippocampus specimens. Compared with the 60% O2 group (memory retention of 86.33% ± 17.52%), the memory of rats in the sev1a and sev1b groups showed a significant decrease (sev1a: 44.29% ± 11.26%; sev1b: 62.42% ± 7.27%; all P<0.05), while the sev1b and sev30b groups showed no significant differences (sev30a: 84.41% ± 14.15%; sev30b: 85.21% ± 11.61%; all P>0.05). Compared with the 60% O2 group (c-fos: 92.83 ± 7.88; p-CREB: 72.22 ± 8.89), the expression of p-CREB and c-fos in hippocampal neurons decreased in the sev1a group (c-fos: 23.13 ± 3.28; p-CREB: 22.88 ± 5.18) and the sev30 group (c-fos: 23.22 ± 3.13; p-CREB: 25.58 ± 2.26) (all P<0.05), while the sev30a and sev30b groups showed no significant differences (all P>0.05). Sevoflurane has a short-term negative stimulating effect on the memory maintenance ability of juvenile rats without an impact based on dosing frequency. Sevoflurane decreases the expression of p-CREB and c-fos in hippocampal neurons of juvenile rats.