[Effects of ketamine and splenectomy on cognition and synaptic plasticity in hippocampus of senile rats]

To study the effects of ketamine anesthesia and surgery on cognition and synaptic structure in hippocampus of senile rats.Fifty-six rats aged 18 months were randomly divided into 3 groups: Groups C (control group), A (ketamine 40 mg/kg, i.p.) and O (ketamine anesthesiasplenectomy). Morris water maze test was used to observe cognition at Days 1, 37 after ketamine anesthesia or operation respectively. Accordingly Groups A and O were divided into 3 subgroup, i.e. A1, A3, A7 and O1, O3, O7. The time of Morris water maze test was recorded and the synaptic structure was measured in the polymorphic layer of the rat hippocampal field CA3.Compared to Group C, the latency period and swimming distance significantly increased in Groups A1, O1 and O3 (P0.05), and the numbers passing the original platform decreased significantly in Groups O1 and O3 (P0.01). The latency period was significantly longer in Group O1 than that in Group A1 (P0.05) while the swimming distance was unchanged. Compared to Group C, the width of synaptic cleft (P0.01) increased, the length and area of postsynaptic densities (P0.05 or P0.01) as well as synaptic curvature (P0.01) decreased in Groups O1 and O3. The percentage of perforated synapses also decreased in Groups O1 and O3.Surgical injury can impair cognition of senile rats and the synaptic plasticity might be involved in postoperative cognitive dysfunction.