Paired Cisterna Magna Nanoinjection and Laser Speckle Contrast Imaging Assay to Study Cerebral Blood Flow Regulation...

Cerebral blood flow (CBF) regulation is crucial for maintaining cognitive functions, but its underlying mechanisms remain poorly understood. Investigating the cellular and molecular processes involved in this regulation requires a pharmacological approach that allows precise drug delivery into cerebral spinal fluid (CSF) while enabling real-time monitoring of cerebral blood flow dynamics. In this paper, we present a method for studying cerebral blood flow regulation in vivo by combining nanoinjector-based intracisternal magna (ICM) injection with laser speckle contrast imaging. The nanoliter injector-based ICM injection technique allows for precise drug delivery at a dynamic range from nL/min to µL/min. In our experiments, this approach significantly reduced the injection volume from the traditional 5-10 μL to just 1.5 μL, thereby maintaining normal intracranial pressure. When combined with laser speckle contrast imaging, we were able to monitor cerebral blood flow (CBF) dynamics in real time before, during, and after ICM injections. Using this method, we evaluated CBF changes in response to ICM injection of three different vasodilators: (S)-3,5-Dihydroxyphenylglycine (DHPG), acetylcholine, and adenosine. While all three vasodilators increased basal CBF, they had distinct effects on CBF dynamics. For instance, adenosine's impact was transient, whereas DHPG and acetylcholine produced long-lasting effects. With its unique advantages, this method represents a valuable addition to the toolbox of studying rodent CBF regulation in vivo.