Effects of laparotomy on cognitive function in rats with traumatic brain injury and the realationship with calcium overload

Abstract

Objective To evaluate the effect of laparotomy on cognitive function in rats with traumatic brain injury and the relationship with calcium overload. Methods One hundred and fifty healthy male Wistar rats, aged 2~3 months, weighing 190~220 g, were assigned into 5 group (n=30 each) using a random number table: blank group(group B), surgery group of blank rats(group BS), surgery group of sham rats(group SS), traumatic brain injury rats group(group T), surgery group of traumatic brain injury rats(group TS). TBI model was made in rats of group T and TS by Feeney method.Rats in group SS were only treated with cranial bone window without crainocerebral impact.Both group B and BS were normal rats. Then the rats in group BS, SS and TS group underwent laparotomy under sevoflurane anesthesia (the operation time was about 3 hours) and the rats in group B and T inhaled pure oxygen for 3 hours after 20 days. One day before surgery, 3 and 7 d after surgery, 10 rats in each group were randomly selected for Morris water maze test. The hippocampus tissue of 10 rats were taken after the water maze test. The apoptosis rate and calcium concentration of hippocampal neurons were measured by flow cytometry, and the expression level of cleaved caspase-3 in hippocampal tissues was determined by Western blot. Results One day before surgery, compared with group B(the escape latency(9.8±0.8)s, the number of crossing platform (5.8±0.8), the apoptosis rate of hippocampal neurons (2.5±0.9)%, calcium ion concentration (2.3±0.2), the expression of cleaved caspase-3 (0.22±0.07) ), the escape latency of group T and group TS were prolonged (group T: (25.5±0.7)s, P<0.05; group TS: (25.1±1.1)s, P<0.05), the number of crossing platform decreased (group T: (2.7±0.8), P<0.05; group TS: (2.8±0.6), P<0.05), the apoptosis rate of hippocampal neurons increased (group T: (5.3±0.6)%, P<0.05; group TS: (5.2±1.0)%, P<0.05), calcium ion concentration increased (group T: (3.7±0.4), P<0.05; group TS: (3.6±0.5), P<0.05) and the expression of cleaved caspase-3 increased (group T: (0.45±0.07), P<0.05; group TS: (0.44±0.05), P<0.05), the differences were statistically significant. Compared with the group SS, the escape latency (3 d after surgery: group SS: (23.8±1.3)s, group TS: (56.4±2.5)s, P<0.05; 7 d after surgery: group SS: (16.6±1.8)s, group TS: (38.1±2.1)s, P<0.05)of the rats in group TS were prolonged, the number of crossing platform decreased (3 d after surgery: group SS: (2.9±0.6) , group TS: (1.1±1.1) , P<0.05; 7 d after surgery: group SS: (4.2±1.2) , group TS: (1.7±1.3), P<0.05), the apoptosis rate of hippocampal neurons (3 d after surgery: group SS: (4.8±0.6)%, group TS: (14.4±0.6)%, P<0.05; 7 d after surgery: group SS: (3.8±1.1)%, group TS: (9.6±1.3)%, P<0.05), calcium ion concentration (3 d after surgery: group SS: (3.1±0.3), group TS: (6.4±0.5), P<0.05; 7 d after surgery: group SS: (2.6±0.3), group TS: (4.8±0.4), P<0.05) , the expression of cleaved caspase-3 (3 d after surgery: group SS: (0.42±0.03), group TS: (0.88±0.08), P<0.05; 7 d after surgery: group SS: (0.33±0.05), group TS: (0.63±0.06), P<0.05) in the hippocampus increased after surgery (P<0.05). Compared with the T group, the escape latency (3 d after surgery: group T: (18.6±2.0)s, group TS: (56.4±2.5)s, P<0.05; 7 d after surgery: group T: (13.8±2.6)s, group TS: (38.1±2.1)s, P<0.05) of the rats in group TS were prolonged, the number of crossing platform (3 d after surgery: group T: (3.4±0.5), group TS: (1.1±1.1), P<0.05; 7 d after surgery: group T: (4.3±1.2), group TS: (1.7±1.3), P<0.05) decreased, the apoptosis rate of hippocampal neurons (3 d after surgery: group T: (4.4±0.7)%, group TS: (14.4±0.6)%, P<0.05; 7 d after surgery: (3.3±1.3)%, group TS: (9.6±1.3)%, P<0.05), calcium ion concentration (3 d after surgery: group T: (3.4±0.4), group TS: (6.4±0.5), P<0.05; 7 d after surgery: group T: (3.0±0.3), group TS: (4.8±0.4), P<0.05), the expression of cleaved caspase-3 (3 d after surgery: group T: (0.40±0.04), group TS: (0.88±0.08), P<0.05; 7 d after surgery: (0.35±0.02), group TS: (0.63±0.06), P<0.05) in the hippocampus increased after surgery(P<0.05). Conclusion Laparotomy can aggravate the cognitive impairment of rats with traumatic brain injury and cause postoperative cognitive impairment, which may be related to the increased degree of calcium overload and the increased rate of hippocampal neuron apoptosis. Key words: Laparotomy; Traumatic brain injury; Postoperative complications; Cognitive impairment