Answer:
Mannitol is a drug that temporarily disrupts tight junctions. This drug is often added to medications that need to get into the extra-cellular fluid of the brain because it will make the capillaries of the blood-brain barrier more permeable to larger molecules.
Step-by-step explanation:
The blood-brain barrier's components are endothelial cells, basement membrane, pericytes, and astrocyte endfeet. The gaps between endothelial cells are small. As a consequence, they form tight junctions that allow the passage of specific and small molecules. In this way, the barrier stops any pathogen from entering the brain. That is to say, that the blood-brain barrier is extremely selective; therefore, medications will not pass through it, so to allow the medicine to enter the brain extracellular fluid, the tight junctions of the endothelial tissue must be disrupted with mannitol.