Introduction: Recently we have shown that docosahexaenoic acid (DHA) is neuroprotective after experimental stroke in young rats. The purpose of this study was to determine whether treatment with DHA would be protective in aged rats after focal cerebral ischemia.
Methods: Isoflurane/nitrous oxide-anesthetized normothermic (brain temperature 36-36.5oC) male Sprague-Dawley aged rats (16-months old) received 2h middle cerebral artery occlusion (MCAo) by poly-L-lysine-coated intraluminal suture. The behavioral function was evaluated during occlusion (60 min), and on days 1, 3 and 7 after MCAo; a grading scale of 0-12 was employed (0=normal and 12=maximal deficit). The agent (DHA, 5 mg/kg; n=6) or vehicle (saline; n=7) was administered i.v. at 3h after MCAo onset. The composite neuroscore comprises two different neurological tests, the postural reflex test and the forelimb placing test, to measure visual, tactile and proprioceptive stimuli, which were evaluated on days 1, 2, 3 and 7. High resolution ex vivo MRI using an 11.7T Bruker was performed on day 7. The core and penumbra were automatically identified using the Hierarchical Region Splitting method for penumbra identification. Histopathology and immunostaining were conducted after completion of MRI on day 7.
Results: DHA treatment improved neurological scores on days 1 (by 18%), 2 (by 25%), 3 (by 22%) and 7 (by 36%). Total, cortical and subcortical lesion volumes computed from T2WI were significantly reduced by DHA treatment (by 62-75%). DHA treatment also reduced cortical, subcortical and total brain infarction (by 65- 80%). In addition, DHA therapy decreased ED-1 positive microglia/microphages (by 62%), GFAP-positive astrocytes (by 21%), and NeuN-positive neurons (by34%), and it increased SMI-71-positive vessels (by 46%) in the ischemic penumbra.
Conclusion: DHA therapy is highly neuroprotective in aged rats following focal cerebral ischemia and has potential for the effective treatment of ischemic stroke in aged individuals.