Characterization of the hemodynamic response in the rat lumbar spinal cord using intrinsic optical imaging and laser speckle.

Quantifying spinal cord functions is crucial for understanding neurophysiological mechanisms governing the intact and the injured spinal cord. Intrinsic optical imaging (IOI) and laser speckle provides measures of deoxyhemoglobin (HbR) and oxyhemoglobin (HbO(2)) concentrations, blood volume (BV) and blood flow (BF) at high spatial and temporal resolution. In this study we used IOI and laser speckle to characterize the hemodynamic response to neuronal activation in the lumbar spinal cord of anaesthetized rats (N=9). We report consistent temporal variations of HbR, HbO(2), BV and BF located ipsilaterally at L3-L5. Responses were significantly higher when stimulation intensity was increased. Vascular changes extended several millimetres from the epicenter, supporting the venous drainage observed in functional magnetic resonance imaging studies.