Seven rats were subjected to a 2-h transient middle cerebral artery occlusion with reperfusion. PET studies were performed longitudinally using [13N]ammonia at 1, 3, 7, 14, 21 and 28 days after cerebral ischemia.
In vivo PET imaging showed a significant increase in [13N]ammonia uptake at 7 days after cerebral ischemia with respect to one day after the occlusion in the cerebral territory irrigated by the MCA in both the ischemic and contralateral hemispheres. This increase was followed by a return to control values at day 28 after ischemia onset. Brain regions located both inside and outside the primary infarct areas showed similar perfusion changes after cerebral ischemia.
[13N]ammonia shows hemodynamic changes after stroke involving hyperperfusion that might be related to angiogenesis and functional recovery. Long-term blood hyperperfusion is found both in ischemic and remote areas to infarction. These results may contribute to a better understanding of the evolution of cerebral ischemic lesion in animal models.