CHARACTERIZATION OF CBF RESPONSE TO SOMATOSENSORY STIMULATION - MODELAND INFLUENCE OF ANESTHETICS

We investigated the cerebral blood flow (CBF) response to somatosensor y stimulation. Stimulation of neuronal activity was performed by defle ction (2-3/s) of the mystacial vibrissae in rats over a period of 60 s , and regional cortical CBF was measured continuously in the contralat eral somatosensory cortex with laser-Droppler flowmetry. CBF within th e somatosensory cortex wag studied through the parietal bone thinned t o translucency (n = 7) or through a closed cranial window with the dur a mater removed (n = 7). In addition, the differential effect of anest hetics (halothane-N2O, n = 5; thiobutabarbiturate, n = 5; and alpha-ch loralose, n = 7) on the CBF response to stimulation was investigated. After a rapid increase after stimulation onset (maximum reached within 2-3 s), CBF remained above baseline with a slight tendency to decreas e despite continued stimulation. On termination of stimulation, CBF fe ll to near prestimulation values within 2-3 s. The following mean CBF responses above baseline during the 60-s stimulation period were obtai ned: halothane-N2O anesthesia, 25.4 +/- 5.9%; thiobutabarbiturate anes thesia, 10.6 +/- 2.4%; and alpha-chloralose anesthesia, 16.9 +/- 2.3 ( through the translucent bone) and 16.2 +/- 2.9% (closed cranial window , dura removed). We conclude that coupling of CBF to neuronal function has a very high temporal resolution (<3 s) and that whisker deflectio n in rats provides a physiological stimulus to study coupling with las er-Doppler flowmetry.