脳幹部血流に対するプロスタグランディンE_1の影響 Effect of Prostaglandin E_1 on Brainstem Blood Flow

Posterior circulation disturbance, commonly known as vertebrobasilar insufficiency (VBI), is often associated with symptoms such as vertigo and instability. These various symptoms are thought to be due to hemodynamic disorders of the vertebrobasilar circulation that temporarily damage the vestibular nucleus (VN) and/or the cochlear nucleus (CN) within the brainstem. In this study, using a Laser-Doppler approach, we investigated the brainstem blood flow (BBF) feeding the vertebrobasilar system in order to estimate the influence of continuous intravenous infusion of prostaglandinE1 (PGE1), which acts as a microvascular dilator, in normal rats in this study. The following results were obtained. 1. During continuous intravenous infusion of PGE1 (at doses of 5 and 10ng/min/kg), no significant fluctuations of physiological parameters (PaO2, PaCO2, pH, saturation, body temperature, mean arterial blood pressure) were observed. However, the mean arterial blood pressure showed a tendency to decline after 45 minutes of continuous infusion of the higher dose (10ng/min/kg). 2. The BBF in the rats increased significantly to about 120% of the initial level after 30 minutes of continuous infusion of PGE1, compared to control infusion of saline. 3. Dose-dependent increases in the BBF were apparent after 60 minutes continuous infusion. Considering the particular construction of the perforating vessels within the brainstem in both the VN and CN, the BBF measured in this investigation sensibly reflects is considered to reliably reflect the blood flow in these two nuclei. Therefore, we conclude that continuous intravenous infusion of PGE1 might be efficacious in cases of vertigo, equilibrium dysfunction and hearing impairment which directly result from circulation disturbances of the brainstem, because PGE1 would increase the blood flow to the VN and CN via improvement of the microvascular circulation within the brainstem.