Spreading Depolarization during the Acute Stage of Experimental Subarachnoid Hemorrhage in Mice

Spreading depolarization (SD) has been suggested as a pathomechanism for delayed cerebral ischemia after subarachnoid hemorrhage (SAH). However, the role of SD during the acute phase of SAH is still unclear. The objective of this study was to investigate (a) the occurrence of SD with intrinsic optical signal (IOS) imaging, (b) the effect of ketamine on SD, and (c) the resulting brain edema (brain water content (BWC)) during the acute stage of experimental SAH in mice. SAH was elicited by the endovascular filament perforation method. After SAH or sham operation, ketamine or saline, 30 mg/kg, was given every half hour. Changes in tissue light reflectance were recorded with IOS. BWC was measured during the acute stage. Overall, 199 SDs occurred in SAH groups and 33 SDs appeared in sham groups. These SDs displayed distinct originating and spreading patterns. Compared with saline, ketamine decreased SD spread and influenced the amplitude, duration, and speed of SD. However, the occurrence of SD was not prevented by ketamine. Moreover, ketamine did not reduce BWC after SAH. These results demonstrate that SD occurs with a high incidence during the acute stage of SAH. SDs are heterogeneous in incidence, origination, and propagation. It remains unclear whether ketamine effects on SD may be viewed as therapeutically beneficial after SAH.