Scientists have long thought that anesthetic drugs might protect the brain during a stroke, but there was no way to rigorously test this idea because triggering strokes in animals requires the use of anesthesia. But now, a team of neuroengineers in China has come up with a work-around. Using lasers and a photosensitive dye, researchers set off strokes without needing to put animals to sleep, allowing them to finally disentangle the role of anesthetics on these often devastating events. The team first installed cranial windows in 22 rats to provide access to a critical artery in the brain. A day later, the neuroscientists injected the rats with a photosensitive dye. Then, by shining a laser on that artery, they could activate the dye to begin clotting, prompting an ischemic stroke -- without having to anesthetize first. Using this method, the researchers triggered strokes in two groups of rats. Half received the anesthetic isoflurane and were asleep, while the other half did not, and were awake. While clots formed within 15 minutes in both sets of animals, real-time laser speckle imaging revealed that more of the brain experienced a big drop in blood flow when rats were conscious. Brain lesions were larger in rats without the drug, and those animals were also more neurologically impaired. The findings suggest that anesthetics alter cerebral blood flow as soon as a stroke begins, and can safeguard the brain from damage. The effects of isoflurane on the neurovascular system are complicated, but as a potent vasodilator, the drug might widen blood vessels and reduce injury when clots starve parts of the brain of food and oxygen. Some neuroprotection may also have to do with changes in neurotransmitter concentration or neuron excitability. Future work using this model should be able to clarify how isoflurane acts to protect the brain during a stroke.