Figure 1.

Experimental block diagram and measurement protocol. (A) Schematic of the experimental setup for monitoring the response of blood flow in intracranial vessels together with other physiological parameters to NTG administration. ABP arterial blood pressure, ECG electrocardiogram, iPPG imaging photoplethysmography. Nitroglycerin cannula was used for intraperitoneal administration of nitroglycerin. Cannulas in femoral vein and artery served for intravenous injection of sumatriptan or equivalent volume of saline, and for ABP monitoring, respectively. Steel needles were inserted into animal’s limbs for ECG recording by digital electrocardiograph. For monitoring of end-tidal CO₂, a carbon dioxide analyzer was used. iPPG module was located above the rat’s brain to assess a reaction of the meningeal vessels through the closed cranial window. (B) Time-line of the experimental protocol. iPPG, ECG, and ABP were simultaneously and synchronously recorded during 30 s in every time point.