Bacopa monnieri Increases Cerebral Blood Flow in Rat Independent of Blood Pressure

Bacopa monnieri (L.) Wettst. (Brahmi in India and Thailand) is an ayurvedic dementia treatment, but its effect on cerebral blood flow (CBF) is still unknown. We sought to test its chronic and acute effects on CBF compared with Ginkgo biloba and donepezil. CBF was measured by laser Doppler from rat cerebral cortex after 8 weeks of daily oral dosing of these drugs. Systolic blood pressure was also measured using the tail cuff method or via arterial cannulation. In rats treated with B. monnieri (40 mg/kg), CBF was 25% increased [2927 +/- 123 perfusion units, (PU)] compared with shams (2337 +/- 217PU, p < 0.05, nine rats). G. biloba (60 mg/kg) also increased CBF (by 29% to 3019 +/- 208 PU, p < 0.05, nine rats). No clear effect was obtained with donepezil (1 mg/kg). Chronic administration of the preparations had no effect on blood pressure. In contrast, intravenous acute infusion of these herbals (2060 mg/kg) had marked dose-dependent hypotensive actions (diastolic similar to 31 mmHg lower with 40 mg/kg of either extract), which correspondingly reduced CBF by similar to 15%. Likewise, CBF fell slightly with acute intravenous sodium nitroprusside and rose with noradrenaline. Donepezil (1 mg/kg) was slightly hypotensive without affecting CBF. Increased CBF with B. monnieri may account for its reported procognitive effect, and its further exploration as an alternative nootropic drug is worthwhile. Copyright (C) 2012 John Wiley & Sons, Ltd.