Cerebral Blood Flow Autoregulation During Hypobaric Hypotension Assessed by Laser Doppler Scanning

Summary: Hypobaric hypotension was used to reduce systemic blood pressure in rats below the lower threshold of CBF autoregulation to evaluate a new laser Doppler (LD) "scanning" technique. Spontaneously breathing male Wi star Kyoto rats (n = 8) were anesthetized with chloral hydrate and the head fixed in a stereotaxic head holder. A cranial window with intact dura mater was in­ troduced to assess local CBF (lCBF) by LD. One station­ ary probe served to detect rapid flow changes, whereas the second probe was used to sample lCBF recordings from many cortical locations by means of a stepping mo­ tor-controlled micromanipulator to obtain lCBF fre­ quency histograms. Advantages are an improved spatial resolution together with the easy detection of low-flow