MAGNETIC-RESONANCE-IMAGING OF PROPAGATING WAVES OF SPREADING DEPRESSION IN THE ANESTHETIZED RAT

Gradient echo magnetic resonance (MR) imaging was used to demonstrate propagating waves of cortical spreading depression (SD) in the anaesth etised rat. SD was initiated by remote perfusion with 150 mM KCl appli ed for 0.5-2 min to the left parietal cortex. Gradient echo MR images were obtained every 12-30 s in either a vertical coronal section or a horizontal section including the superficial cortex in plan view. With in 2 min of application of KCl, we observed a zone of increased signal intensity (3-15%) on the MR image, up to 2 mm across, lasting approxi mately 1 min and propagating away from the site of initiation. The mea n velocity for 27 of such waves seen in seven animals was calculated t o be 2.79 mm/min, with means (+/-SD) in individual animals averaging 2 .90 +/- 0.46 mm/min (n = 7). Increased signal intensity in gradient ec ho images has been attributed to an increased level of oxygenation wit hin the venous blood. Our results are consistent with this interpretat ion although other physiological changes during SD may also contribute to the signal changes.