Regional cerebral blood flow responses to variable frequency whisker stimulation: an autoradiographic analysis

Activation of the rat primary somatosensory barrel field (S1BF) is a common ly used model to study the mechanisms of evoked coupled cortical blood flow changes. However, the relationship between these blood Row changes and var iable whisker movement has not been completely characterized. We have previ ously shown that in urethane anesthetized rats, the magnitude of laser-Dopp ler measured cortical blood how changes increase linearly with the frequenc y of full Dad whisker movement over the physiological range of 1.5 to 10.5 s. To further test the hypothesis that local cortical blood flow increases with frequency of whisker movement and underlying neuronal activity, region al cerebral blood Row (rCBF) was determined autoradiographically in seven u rethane anesthetized SD rats. Selected rows of whiskers (rows C, D, E) were stimulated at 3 s on the right side of the rat's face and simultaneously a t 10 s on the left side for 2 min prior to radioactive tracer administratio n, Subregions of somatosensory cortex were identified with the aid of thion in and cytochrome oxidase stained sections. Mean rCBF (ml/100 g/min) for S1 BF were: S1BF [0 s] left cortex, 146+/-13; S1BF [0 s] right cortex, 158+/-1 5; S1BF[3 s], 160+/-13; S1BF [10 s] 178+/-14. In both stimulated and nonsti mulated regions, the profile of blood flow increased across cortex laminae, peaking in layer IV and decreasing through deeper layers. Maximal blood fl ow increases elicited by whisker movement occurred in cortical layers I-IV. These data support the hypothesis that whisker movement elicited rCBF chan ges are input frequency dependent and are most pronounced in cortical layer s I though IV. These data provide a strong framework in which to study the mechanisms of neuronal activity-blood flow coupling. (C) 2000 Elsevier Scie nce B.V. All rights reserved.