Hemodynamics evoked by microelectrical direct stimulation in rat somatosensory cortex

The aim of this: study was to estimate the timing (latency) of the increase in red blood cell (RBC) velocity and RBC concentration, and the magnitude of response in local cerebral blood flow (LCBF) for neuronal activation. We measured LCBF change during activation of the somatosensory cortex by dire ct microelectrical stimulation. Electrical stimuli of 5, 10 and 50 Hz of 1 ms pulse with 10-15 mu A: were given for 5 s. LCBF, RBC velocity and RBC co ncentration were monitored by laser-Doppler flowmetry (LDF) in alpha-chlora lose anesthetized rats (n = 7). LCBF, RBC velocity and RBC concentration in creased nearly proportionally to stimulus frequency, i.e. neuronal activity . LCBF rose approximate to 0.5 s after the onset of stimulation, and there was no significant time lag of the latencies among LCBF, RBC velocity and R BC concentration at the same stimulus frequency. We interpret these results to mean that the onset of LCBF increase on cortical activation is reflecte d by a rapid change in arteriole (resistance vessel) dilation and capillary volume. The data also elucidate the linear relationship between LCBF incre ase and cortical activity. (C) 1999 Elsevier Science Inc. All rights reserv ed.