LCBF changes in rat somatosensory cortex during whisker stimulation monitored by dynamic H-2 clearance

We evaluated increases in local cerebral blood flow (LCBF) localized to single activated cortical columns by H-2 clearance methods. The rat whisker-barrel cortex is a model for cortical function and neural processing in active explorative behaviors. Up to four 30-40 mu m Pt wire electrodes were inserted in or near the rat whisker-barrel cortex. Electrode positions were mapped by postmortem histology. H-2 was generated electrochemically by constant current from one electrode and detected by one or more other electrodes 300-500 mu m away. Changes in LCBF produced inverse changes in PH2. Shifts during steady H-2 generation were calibrated against standard H2 inhalation clearance curves at rest and during inhalation of 7.5% CO2 for 1 min for quantitative estimates of LCBF. Contralateral whisker stimulation at 3 Hz, 1 min duration and delivered every 2 min produced the largest increases in LCBF. LCBF responses were detected in approximate to 1 s. Stimulation of single whiskers produced the largest responses when an electrode was in the corresponding barrel. These results indicate that increased neural activity in a single cortical column produces blood flow responses primarily in that column.