Intravital fluorescence microscopy for the study of blood-brain-barrier function

Area of Science:

• Neuroscience
• Physiology
• Biomedical Engineering

Background:

• The blood-brain barrier (BBB) protects the central nervous system but its permeability can be altered in various conditions.
• Understanding the mechanisms of BBB opening is crucial for developing effective treatments for neurological disorders.

Purpose of the Study:

• To investigate the dynamic changes in vascular diameters and BBB function in the feline parietal cortex.
• To determine if BBB opening can occur independently of vasodilation.
• To establish a suitable experimental model for in vivo analysis of cerebral vascular dynamics.

Main Methods:

• Utilized an open skull window technique and intravital fluorescence microscopy in cats.
• Superfused the cortical surface with artificial cerebrospinal fluid containing bradykinin (BK), Na+-arachidonate (AA), or xanthine-oxidase (XO).
• Administered intravenous tracers of varying molecular sizes (Na+-fluorescein, FITC-albumin, FITC-dextran) to assess BBB permeability.

Main Results:

• Bradykinin (BK) and Na+-arachidonate (AA) induced venular leakage, indicating increased BBB permeability, without significant vasodilation.
• Xanthine-oxidase (XO) caused marked cerebral vasodilation but did not induce extravasation.
• Control experiments showed that prolonged light exposure could affect microcirculation and BBB integrity.

Conclusions:

• BBB opening can be dissociated from vasodilatory responses.
• The experimental model allows simultaneous analysis of dynamic changes in cerebral vessel permeability and vasomotor behavior.
• This model is suitable for studying physiological and pathological conditions affecting the brain vasculature.