The therapeutic effect of Ginkgo biloba extract in SHR rats and its possible mechanisms based on cerebral microvascular flow and vasomotion

This paper aimed to investigate the therapeutic effect of an extract of Gin kgo biloba leaves (EGb 761) on hypertension and its possible mechanisms in the view of cerebral microcirculation. Twenty normotensive rats and 24 SHR rats were used. Surgical preparation was made to produce a cranial window f or observation of the capillary network on the cerebral cortex. The intravi tal videomicroscopy equipped with digital image processing system and laser Doppler flowmeter were used for this study. The arterial blood pressure, r ed cell velocity (V), microvacular diameter (D), number of open capillaries (OCN), circulating endothelial cells (CEC) in blood, relative blood flow ( Flow) and frequency (Fc), amplitude (AMP) of vasomotion were measured. The obtained data were compared between EGb-treated rats that received per os 1 00 mg/kg/d for 9 days and placebo control rats. Untreated SHR rats showed very severe dysfunction in the microcirculation w ith high blood pressure (213+/-16.7 mmHg). The blood pressure decreased sig nificantly to 153 +/- 20 mmHg in EGb-treated SHRs group, compared with thos e of untreated rats (p < 0.01). Both normotensive and hypertensive rats inc reased the blood flow velocity and LDF flow after EGb-treatment. The vasomo tion property, the CEC and OCN changed greatly in EGb-treated SHR rats, but no significant difference was observed in normotensive rats. It was sugges ted that EGb 761 had therapeutic effect on SHR rats by increasing blood per fusion, regulating vasomotion function, opening efficiently capillaries and releasing the peripheral resistance. The injured vascular endothelium of S HR rats was also partly reversed by EGb-treatment. It was concluded that EG b 761 could be used to regulate hypertension and to protect the cerebral mi crocirculatory function.