Alpha-chloralose is a suitable anesthetic for chronic focal cerebral ischemia studies in the rat: a comparative study

alpha-Chloralose is widely used as an anesthetic in studies of the cerebrovasculature because it provides robust metabolic and hemodynamic responses to functional stimulation. However, there have been no controlled studies of focal ischemia in the rat under alpha-chloralose anesthesia. Artificially ventilated rats were prepared using 1.2-1.5% isoflurane anesthesia for filament occlusion of the right middle cerebral artery (MCA), and anesthesia was either switched to alpha-chloralose (60 mg/kg bolus, 30 mg/kg/h; n=10) or was maintained on 1% isoflurane (n=10). Following temporary MCA occlusion EEG was monitored from a screw electrode and changes in cerebral blood flow (rCBF) measured with a laser Doppler probe placed over the ischemic cortex. This study shows that alpha-chloralose is a safe anesthetic for ischemia studies and provides excellent survival. Compared with isoflurane, the cortical and total infarct volumes are larger in the alpha-chloralose-anesthetized animals, while the functional outcome at 72 h is similar. The total duration of peri-infarct flow transients (PIFTs) is also significantly longer in alpha-chloralose-anesthetized animals. The average amplitude of the flow transients showed a good correlation with the extent of edema in all animals as did the total duration of non-convulsive seizures (NCS) in the alpha-chloralose-anesthetized animals.