SBA 3517 - theguidewire

Route

Examples

Free Membrane Diffusion

Small Lipophilic molecules and gases:

Membrane Channels

Small ions and water:

Carrier-Mediated Transport

Energy transport systems:
- Glucose (GLUT-1)
- Lactate, pyruvate (MCT1)
- Creatine (CrT)
Amino acid transport systems
- Large neural amino acids (LAT1)
- Neurotransmitter precursors

Receptor-Mediated Transport (via transcytosis)

Adsorption mediated transport (via transcytosis)

Factors that increase the rate of transfer across the blood–brain barrier include:

Catecholamines

A number of catecholamines (such as noradrenaline and dopamine) act as neurotransmitters in the central nervous system
Unregulated entry across the blood brain barrier can result in permanent neuroexcitatory damage

Amino acids

Similarly to catecholamines a number of amino-acids (such as glycine and glutamic acid) act as neurotransmitters in the central nervous system
Unregulated entry across the blood brain barrier can result in permanent neuroexcitatory damage

Ammonia (NH₃)

Ammonia is potentially neurotoxic in significant concentrations
It is a small lipophilic molecule which may be expected to cross the BBB
It is rapidly metabolised by the enzymatic barrier to glutamine, preventing passage across the BBB in relevant quantities

Macromolecules

Plasma proteins such as albumin and plasminogen are damaging to nervous tissue and can lead to apoptosis
The BBB prevents passage of such molecules leading to low CSF levels
Results in a lower ability to buffer changes in pH

Charged Ions

The BBB is impermeable to H⁺ and HCO₃^- ions due to their charge
However it is permeable to CO₂ which can pass freely through into the CSF
In this way CO2 from arterial blood can become converted in to H⁺ and HCO₃^- ions which become trapped lowering the pH of CSF

Opioid Analgesics

Anaesthetic Agents

Anetiepileptics

Antidepressants

CNS Stimulants

Antibiotics