Traumatic brain injury (TBI) triggers a complex series of inflammatory responses that contribute to secondary tissue damage. The aim of this study was to investigate the effect of baicalein, a flavonoid possessing potent anti‐inflammatory properties, on functional and histological outcomes and inflammatory cytokine expression, following TBI in rats.

Rats subjected to controlled cortical impact injury were injected with baicalein (30 mg kg⁻¹) or vehicle immediately after injury or daily for 4 days. Neurological status was evaluated using the rotarod, adhesive removal, modified neurological severity scores and beam walk tests. Contusion volume and neuronal degeneration were measured using cresyl violet and FluoroJade B (FJB) histochemistry. Levels of tumour necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β) and interleukin‐6 (IL‐6) mRNA and protein were assessed by real‐time quantitative reverse transcriptase‐PCR, enzyme‐linked immunosorbent assay and immunohistochemistry.

Single‐dose and multiple‐dose treatment with baicalein significantly improved functional recovery and reduced contusion volumes up to day 28 post‐injury, although multiple‐dose baicalein was the more effective treatment. Single‐dose baicalein also significantly reduced the number of degenerating neurons (31%) on post‐injury day 1 as indicated by FJB staining. These changes were associated with significantly decreased levels, at the contusion site, of TNF‐α, IL‐1β and IL‐6 mRNA at 6 h, and cytokine protein on day 1 post‐injury.

Post‐injury treatment with baicalein improved functional and histological outcomes and reduced induction of proinflammatory cytokines in rat TBI. The neuroprotective effect of baicalein may be related to a decreased inflammatory response following the injury.

British Journal of Pharmacology (2008) 155, 1279–1296; doi:10.1038/bjp.2008.345; published online 8 September 2008