Effect of behavioral activity on hemodynamic responses induced by whisker stimulation in awake mice.

In this study, we measured cerebral blood flow (CBF) in awake mice with laser-Doppler flowmetry (LDF). A total of fifteen male C57BL/6J mice were prepared for attaching a custom-made metal head plate to the skull with dental acrylic under isoflurane anesthesia. One day after the surgery, the mice were tethered by screwing the head plate onto a metal rod. Below the animals, a styrofoam ball supported by a jet of air was set in the apparatus. The styrofoam ball freely rotated while the mice walked on it. Regional CBF in the somatosensory cortex and an amount of walking were concurrently monitored with L DF and an optical motion sensor that detect a rotation distance of the ball, respectively. Whisker stimulation (frequency 10 Hz and duration 20 sec) was induced a contra-lateral side of the measurement site. Firstly, whisker stimulation-induced blood flow response and behavior were measured during daytime and nighttime. The blood flow responses showed no significant differences between daytime and nighttime (24% and 23% of the pre-stimulus baseline, respectively), whereas the amount of walking was 22% higher under nighttime relative to daytime. Secondly, the blood flow response and behavior were measured from the same single animal over 7days. The mean coefficient of variance among multiple days was observed to be 0.11 (0.08 to 0.16) and 0.84 (0.52 t o 1.51) for blood flow response and amount of walking, respectively. These results indicate that blood flow response is a relatively stable and reproducible between daytime and nighttime and across multiple days, although amount of walking shows large variations. In conclusion, our system is feasible for a longitudinal study in awake animals.NEURO 201