STIMULATION OF THE NUCLEUS BASALIS OF MEYNERT INCREASES CORTICAL CEREBRAL BLOOD-FLOW WITHOUT INFLUENCING DIAMETER OF THE PIAL ARTERY IN RATS

The effects of focal electrical stimulation of the nucleus basalis of Meynert (NBM) and hypercapnia on diameter of the pial artery and regional cerebral blood flow (CBF) in the parietal cortex were examined in urethane-anesthetized rats. The diameter of pial artery was measured using the video microscope and cortical CBF was measured using the laser Doppler flowmetry. Hypercapnia at 10% of end-tidal CO2 concentration caused significant increases in diameter of the pial artery and cortical CBF. Electrical stimulation of the NBM (with parameters of 200-mu-A, 50 Hz, 0.5 ms. for 1 min) produced a significant increase in cortical CBF, but did not influence the diameter of pial artery. The results suggest that cholinergic fibers originating in the NBM do not contribute to neural vasodilatation of the pial artery, although they induce neural vasodilatation of parenchymal blood vessels which results in an increase in CBF in the parietal cortex.