Functional MRI of delayed chronic lithium treatment in rat focal cerebral ischemia.
OBJECTIVE
The use of lithium as a neuroprotective agent has been demonstrated using various models in which improvements in infarct size, DNA damage, and neurological function were reported. We further investigated neurohemodynamic aspects of the treatment-associated recovery by assessing the therapeutic efficacy of delayed chronic lithium treatment using functional MRI.


METHODS
Ipsilesional functional MRI activations in the somatosensory cortex, acquired 2 weeks after the 90-minute transient middle cerebral artery occlusion, were compared between lithium- and saline-treated rats. Specifically, MRI signal changes based on blood oxygenation level dependence and functional cerebral blood volume responses were examined using electrical stimulation of forelimbs. Additional immunohistochemical assays were performed.


RESULTS
The ratio of ipsilesional to contralesional blood oxygenation level dependence response magnitudes significantly improved with lithium treatments. In contrast, the increase of the functional cerebral blood volume response magnitude ratio was not statistically significant. Nonetheless, the lithium treatment induced significant enhancements of total functional MRI activation (defined as a product of activation volume and response magnitude) for both blood oxygenation level dependence and functional cerebral blood volume methods. Increased cerebral blood volume in periinfarct tissues suggests a possible stroke-induced vascular transformation in both saline- and lithium-treated rats; however, other MRI-derived vascular parameters (vascular size index and microvascular volume) and immunohistochemical staining (CD31, glia fibrillary-associated protein, and matrix metalloproteinase-9) may imply that the neoformation of vasculature was differently affected by the lithium treatment.


CONCLUSIONS
The delayed chronic lithium treatment enhanced the blood oxygenation level dependence functional MRI response magnitude in the absence of neurological improvement and influenced vascular formation in poststroke animal models.
Kim
Young R
YR
Athinoula Martinos Center for Biomedical Imaging/Massachusetts General Hospital, 149 13th Street, Room 2301, Charlestown, MA 02129, USA. spmn@nmr.mgh.harvard.edu
van Meer
Maurits P A
MP
Tejima
Emiri
E
Murata
Yoshi
Y
Mandeville
Joseph B
JB
Dai
George
G
Chuang
De-Maw
DM
Rosen
Bruce R
BR
Lo
Eng H
EH
D000818:Animals; D002545:Brain Ischemia / Q000188:drug therapy*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004195:Disease Models, Animal; D020244:Infarction, Middle Cerebral Artery / Q000188:drug therapy*; D018021:Lithium Chloride / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley
D018696:Neuroprotective Agents; D018021:Lithium Chloride; D010100:Oxygen