Blood Brain Barrier

BBB structure

tight junctions between endothelial cells (non-fenestrated)

prevents entry

proteins and other water-soluble low-molecular-weight substances

entry related

lipid solubility

neuron signaling reliance

electrical signals and fine chemical signals

protection

from unwanted chemicals in the blood that can disrupt the fine-tuned neuronal signaling

95% drugs

amount of drugs that do not show useful activity in the brain and many show poor penetration into the brain

downside of lipophilic drugs

it will penetrate every organ and cell of the body

small drugs transportation

transported by “nutrient transport system”

use of efflux transporters

quickly expel small drugs

6 mechanisms that exist for vital molecules to cross the barrier

• transcellular lipophilic pathway

• paracellular pathway

• transport proteins

• receptor-mediated transcytosis

• adsorptive transcytosis

• efflux

ultrasound effect on BBB

can disrupt the barrier and allow magnetic particles to be guided through the barrier

injection of hyperosmotic solution

• draws water out of the endothelial cells causing them to shrink

  • pulls apart the tight junction, forming gaps for diffusion of drugs