Scalp mechanical stimulation promotes moderate vasodilation and the permeability of blood-brain barrier in anesthetized mice

OBJECTIVE Scalp mechanical stimulation, like combing, is one of the useful methods to keep brain health, which was historically recorded in traditional Chinese medicine thousand years ago. For the brain care, it is considered to promote cerebrovascular circulation to prevent alopecia,headache, neurasthenia, insomnia, memory deficits. However, few study was reported on its effect and how the scalp mechanical stimulation works on vascular functions. Therefore, in this study, we try to illustrate the effect of combing on the cerebrovascular. METHODS In vivo, the anesthetized mice have been used to observe the effects of scalp mechanical stimulation. Infrared thermal imaging has been used to measure the skin temperature;vasodilation has been evaluated by retro-orbital injection of FITC-dextran 150 ku;the permeability of Blood-Brain Barrier(BBB) was analyzed by confocal microscopy of FITC-dextran 40 ku extravasation and a spectrofluorometric assay of Even Blue extravasation.RESLUTS We found that scalp mechanical stimulation rather than on the back can maintain the body temperature, especially raise the temperature in the ears. Accordingly, a moderate vasodilatation of auricles′ capillaries(≤ 8 μm) was observed, the phenomenon of which did not occur combing on the back. Furthermore, the permeability of BBB was promoted by the assays of small molecular extravasation. In addition, in vivo imaging, the small molecular of FITC-dextran(40 ku) was found to transport far away from the blood vessels into the brain parenchyma with the lapse of time. CONCLUSION Scalp mechanical stimulation can work on vasodilatation of auricles and promotion of BBB under a biological condition. Combing, as a daily behavior, simple but may yield novel insights into neuroprotection.