Parenchymal spin-lock fMRI signals associated with cortical spreading depression.
We found novel types of parenchymal functional magnetic resonance imaging (fMRI) signals in the rat brain during large increases in metabolism. Cortical spreading depression (CSD), a self-propagating wave of cellular activation, is associated with several pathologic conditions such as migraine and stroke. It was used as a paradigm to evoke transient neuronal depolarization leading to enhanced energy consumption. Activation of CSD was investigated using spin-lock (SL), diffusion, blood oxygenation level-dependent and cerebral blood volume fMRI techniques. Our results show that the SL-fMRI signal is generated by endogenous parenchymal mechanisms during CSD propagation, and these mechanisms are not associated with hemodynamic changes or cellular swelling. Protein phantoms suggest that pH change alone does not explain the observed SL-fMRI signal changes. However, increased amounts of inorganic phosphates released from high-energy phosphates combined with pH changes may produce SL- power-dependent longitudinal relaxation in the rotating frame (R₁ρ) changes in protein phantoms that are similar to those observed during CSD, as seen before in acute ischemia under our experimental conditions. This links SL-fMRI changes intimately to energy metabolism and supports the use of the SL technique as a new, promising functional approach for noninvasive imaging of metabolic transitions in the active or pathologic brain.
1] Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland [2] Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
Joonas A
JA
Autio
Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland.
Artem
A
Shatillo
Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland.
Rashid
R
Giniatullin
Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland.
Olli H
OH
Gröhn
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001810:Blood Volume; D002540:Cerebral Cortex / Q000098:blood supply / Q000502:physiology*; D002560:Cerebrovascular Circulation; D013181:Cortical Spreading Depression; D006439:Hemodynamics; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010710:Phosphates / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D010710:Phosphates; D000241:Adenosine