General anesthesia is commonly used in experiments; however, its effects on cerebral circulation remain unknown. We measured cerebral blood flow using N-isopropyl[methyl 1,3-14C] p-iodoamphetamine (14C-IMP) and glucose utilization using 2-[1-14C] deoxy-D-glucose during general anesthesia with pentobarbital and chloral hydrate as well as conscious controls using rats and in-vivo autoradiography. Although a substantial reduction in 14C-IMP uptake was seen in the pentobarbital group, there was a significant increase in the chloral hydrate group. The ratio of cerebral blood flow against cerebral glucose utilization was 0.58 over all regions in the pentobarbital group, similar to the value for the controls, whereas this value was significantly high (over 1.5) in the chloral hydrate group. This decoupling effect should be considered when extrapolating experimental study data to normal physiology.