Irradiation attenuates neurogenesis and exacerbates ischemia-induced deficits.

Increased neurogenesis after cerebral ischemia suggests that functional recovery after stroke may be attributed, in part, to neural regeneration. In this study, we investigated the role of neurogenesis in the behavioral performance of gerbils after cerebral global ischemia. We used ionizing radiation to decrease neural regeneration, and 2 weeks later cerebral global ischemia was induced by bilateral common carotid artery occlusion. One month after the occlusion, the animals were behaviorally tested. Irradiation alone reduced neurogenesis but did not change vascular or dendritic morphology at the time of behavioral testing. Neither did irradiation, ischemia, or combined treatment impair rotor-rod performance or alter open-field activity. Gerbils subjected to both irradiation and ischemia demonstrated impaired performance in the water-maze task, compared with those that received only ischemia, radiation, or no treatment. These impairments after cerebral global ischemia under conditions of reduced neurogenesis support a role for the production of new cells in mediating functional recovery.