The blood-brain barrier (BBB) is highly restrictive of the transport of substances between blood and the central nervous system. Brain pericytes are one of the important cellular constituents of the BBB and are multifunctional, polymorphic cells that lie within the microvessel basal lamina. The present study aimed to evaluate the role of pericytes in the mediation of BBB disruption using a lipopolysaccharide (LPS)-induced model of septic encephalopathy in mice. ICR mice were injected intraperitoneally with LPS or saline and were sacrificed at 1, 3, 6, and 24 h after injection. Sodium fluorescein accumulated with time in the hippocampus after LPS injection; this hyperpermeability was supported by detecting the extravasation of fibrinogen. Microglia were activated and the number of microglia increased with time after LPS injection. LPS-treated mice exhibited a broken basal lamina and pericyte detachment from the basal lamina at 6-24 h after LPS injection. The disorganization in the pericyte and basal lamina unit was well correlated with increased microglial activation and increased cerebrovascular permeability in LPS-treated mice. These findings suggest that pericyte detachment and microglial activation may be involved in the mediation of BBB disruption due to inflammatory responses in the damaged brain.