Nutrient transport and the blood-brain barrier in developing animals

Area of Science:

• Neuroscience
• Developmental Biology
• Physiology

Background:

• The blood-brain barrier (BBB) protects the developing brain.
• Neonatal BBB exhibits unique structural features like irregular capillary folds.
• Early BBB development involves significant structural and functional modulations.

Purpose of the Study:

• To investigate structural alterations in the developing rat cortex BBB.
• To characterize the kinetic properties of BBB nutrient transport systems in developing rabbits.
• To compare BBB nutrient transport in newborn versus weanling rabbits.

Main Methods:

• Analysis of capillary profiles in rat cortex.
• Kinetic characterization of BBB nutrient transport systems (purine bases, amino acids, amines, monocarboxylic acids, hexoses) in newborn and weanling rabbits.
• Comparison of transport kinetics between different age groups.

Main Results:

• Rat cortical capillaries transition from irregular neonatal forms to smooth adult-like structures by 21 days.
• All major BBB nutrient transport systems are functional at birth in rabbits, indicating a mature BBB regarding nutrient regulation.
• Transport systems for amino acids, amines, monocarboxylic acids, and hexoses show developmental changes in affinity and capacity, optimizing metabolite supply to the brain.
• A low-affinity, high-capacity monocarboxylic acid transporter at birth shifts to high-affinity, low-capacity by 28 days.
• Glucose transport shifts from high-affinity in newborns to lower-affinity, high-capacity in 28-day-old rabbits.

Conclusions:

• The developing BBB exhibits significant structural and functional adaptations.
• The rabbit BBB is functionally mature at birth concerning nutrient transport regulation.
• Developmental changes in BBB transport kinetics ensure adequate nutrient supply to the growing brain, particularly under conditions of elevated plasma metabolite levels.