Background: Postoperative Cognitive Dysfunction (POCD) has received considerable
attention as one of the main postoperative complications. The underlying mechanism of POCD in
elderly subjects has not been fully elucidated to date. The Central Nervous System (CNS) is isolated
from the bloodstream by the Blood Brain Barrier (BBB) that consists of endothelial cells,
capillary blood vessels and tight junctions. The tight junctions carry out significant biological functions
that are associated with the CNS and blood circulation.
Methods: In this review, I present a hypothesis that blood-brain barrier disruption leads to postoperative
cognitive dysfunction. A total of 81 healthy male Wistar rats were used for the present
study. All the experimental animals were randomly divided into 3 groups: normal control group,
isoflurane group and splenectomy group. The control group was not subjected to any form of treatment.
The rats in isoflurane group were given 1.5-2% isoflurane under intubation and mechanical
ventilation. The rats in splenectomy group underwent splenectomy under the same anesthesia as the
isoflurane group. The Morris water maze was used to examine the learning and memory ability of
the animals. The expression of the Tight Junctions Proteins (TJPs) in the hippocampus was analyzed
using Western blotting. The concentration of Evans Blue (EB) in the supernatant was analyzed
using UV spectroscopy. Ultrastructure changes in the basal laminas, the Tight Junctions
(TJs), mitochondria and the endoplasmic reticulum surrounding the capillaries were assessed by
Transmission Electron Microscopy (TEM).
Results: Following splenectomy, the rats displayed concomitant significant cognitive deficits in the
Morris water maze test. Taken together, the results indicate that the expression levels of occludin
(65KD) following splenectomy were reduced on days one and three in aged rats. No significant
difference was noted in the expression levels of claudin-5, except for a reduction after surgery on
day one. The leakage of EB was higher following splenectomy than control group and isoflurane
group. The ultrastructure of the neurovascular unit was monitored on the day prior to surgery and
on the 1st, 3rd and 7th day following surgery using a transmission electronmicroscope.
Conclusion: The alterations in the levels of tight junction proteins following splenectomy may
contribute to the BBB permeability increase, which in turn will induce postoperative cognitive dysfunction.