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

Abstract

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 μm 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 μm away. Changes in LCBF produced inverse changes in PH 2. Shifts during steady H 2 generation were calibrated against standard H 2 inhalation clearance curves at rest and during inhalation of 7.5% CO 2 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 ≈ 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.