TIA model is attainable in Wistar rats by intraluminal occlusion of the MCA for 10 min or shorter

Abstract

Transient ischemic attack (TIA) has received only little attention in the experimental research field. Recently, we introduced a TIA model for mice, and here we set similar principles for simulating this human condition in Wistar rats. In the model: 1) transient nature of the event is ensured, and 2) 24h after the event animals are free from any sensorimotor deficit and from any detectable lesion by magnetic resonance imaging (MRI). Animals experienced varying durations of ischemia (5, 10, 12.5, 15, 25, and 30min, n=6–8pergroup) by intraluminal middle cerebral artery occlusion (MCAO). Ischemia severity and reperfusion rates were controlled by cerebral blood flow measurements. Sensorimotor neurological evaluations and MRI at 24h differentiated between TIA and ischemic stroke. Hematoxylin and eosin staining and apoptotic cell counts revealed pathological correlates of the event. We found that already 12.5min of ischemia was long enough to induce ischemic stroke in Wistar rats. Ten min or shorter durations induced neither gross neurological deficits nor infarcts visible on MRI, but histologically caused selective neuronal necrosis. A separate group of animals with 10min of ischemia followed up to 1week after reperfusion remained free of infarction and any MRI signal change. Thus, 10min or shorter focal cerebral ischemia induced by intraluminal MCAO in Wistar rats provides a clinically relevant TIA the rat. This model is useful for studying molecular correlates of TIA.