A new method for continuous measurement of regional cerebral blood flow using laser Doppler flowmetry in a conscious rat.

We have developed a new system to continuously measure regional cerebral blood flow (rCBF) in the cortex of a conscious animal. For this purpose, we used rats and laser Doppler flowmetry. Under pentobarbital anesthesia, the animal's skull was opened making a small square hole 3 mm x 3 mm in size. A transparent acrylic plate was placed over the hole in the skull. A polyethylene cannula (inner diameter 1.0 mm, length 5.0 mm) was fixed on the plate as a guide for the laser Doppler flowmeter (LDF) probe (outer diameter 1.0 mm, length 5.5 mm). Both the plate and guide cannula were fixed to the skull by dental cement. Every day for the following two weeks after surgery, the conscious animal was placed in a hammock for recording rCBF. A LDF probe was freely attachable to the plate above the cortex via the guide cannula during measurement of rCBF. The rats were kept in a hammock with their legs firmly touching the floor during measurement of rCBF. It was possible to measure rCBF every day for about two weeks, and rCBF responded consistently to inhalation of 7% CO2 when the responses were expressed as percentages of the prestimulus control rCBF values. This system is recommended for the continuous measurement of rCBF in a conscious animal.