SIMULTANEOUS MEASUREMENTS OF PIAL ARTERIOLAR DIAMETER AND LASER-DOPPLER FLOW DURING SOMATOSENSORY STIMULATION

We simultaneously measured pial arteriolar diameter and changes in cor tical blood flow during activation of the somatosensory cortex by scia tic nerve stimulation. The pial vasculature was visualized with a clos ed-cranial window technique in chloralose-anesthetized rats (n = 13). Local blood flow was monitored with laser-Doppler flowmetry. During st imulation of the sciatic nerve (0.2 V, 5 Hz, 20 s), vascular diameter and laser-Doppler flow consistently displayed similar response profile s. With 0.5-ms stimulation pulses, the responses showed an initial pea k followed by a smaller but sustained plateau dilation. In contrast, 5 -ms pulses evoked a monotonically rising response. Our results support the concept that pial arteriolar diameter changes reflect cortical bl ood flow responses during somatosensory stimulation.