HIGH-RESOLUTION FUNCTIONAL MAGNETIC-RESONANCE-IMAGING OF THE RAT-BRAIN - MAPPING CHANGES IN CEREBRAL BLOOD-VOLUME USING IRON-OXIDE CONTRAST-MEDIA

Contrast-enhanced magnetic resonance imaging was used to produce high- resolution activation maps reflecting local changes in cerebral blood volume after a simple sensory stimulus. Activation of the forelimb reg ion of the somatosensory cortex was performed in alpha-chloralose-anae sthetized rats with an electrical stimulus (5 V, 3 Hz) delivered throu gh needle electrodes placed subcutaneously on the left forelimb. A gra dient echo magnetic resonance imaging sequence, sensitive to changes i n the relative amount of deoxyhemoglobin within the cerebral vasculatu re, produced a 4.05% +/- 1.69% increase in signal intensity. This effe ct was enhanced with an injection of an intravascular iron oxide contr ast agent (Combidex, Advanced Magnetics), resulting in a 9.11% +/- 1.5 2% decrease in signal intensity.