How do substances cross the blood-brain barrier and which substances pass by each route?

Route
Examples
Free Membrane Diffusion
Small Lipophilic molecules and gases:
  • O2, CO2
  • Anaesthetics
  • Ethanol, nicotine
Membrane Channels
Small ions and water:
  • H2O
  • Na, K+, Cl-
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)
  • Insulin
  • Leptin
  • IgG
  • TNFa
Adsorption mediated transport (via transcytosis)
  • Histone
  • Albumin