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Developmental modulations of blood-brain barrier permeability as an indicator of changing nutritional requirements in
Insights
The blood-brain barrier
Area of Science:
- Neuroscience
- Developmental Biology
- Physiology
Background:
- The blood-brain barrier (BBB) regulates the passage of substances into the brain.
- Understanding age-related changes in BBB function is crucial for developmental neuroscience.
Purpose of the Study:
- To investigate age-dependent alterations in the transport of specific metabolites across the blood-brain barrier in rabbits.
Main Methods:
- Intracarotid injection technique was used in rabbits of various ages (newborn to adult).
- Brain uptake index (BUI) was measured for adenine, arginine, choline, lactate, tryptophan, glucose, and butanol.
Main Results:
- Metabolite transport across the BBB varies significantly with age.
- Lactate uptake peaked at 7 days postpartum, while other metabolites (adenine, arginine, choline, tryptophan) showed decreased uptake with age.
- Transport changes were metabolite-specific and independent of blood flow alterations.
Conclusions:
- The blood-brain barrier exhibits dynamic, age-related changes in permeability to essential metabolites.
- These findings highlight the developmental maturation of BBB transport mechanisms for specific nutrients and neurotransmitter precursors.
Abstract:
The intracarotid injection technique has been utilized to examine blood-brain barrier function in studies of newborn (greater than 24 h), 7, 14, 21 and 28 day-old, as well as adult rabbits. The age-related modulations in blood-brain barrier transport of adenine, arginine, choline, lactate and tryptophan were defined and demonstrated to be independent of each other. Lactic acid uptake was unusual in that the brain uptake index (BUI) was found to be greatest at 7 days postpartum. Elevated lactate uptake continues until 14 days and is then reduced. As indicated below, for all of the other metabolites examined, a maximal BUI was observed in the newborn brain and BUIs typically showed some sort of inverse relationship to animal age. The BUI of arginine is apparently halved in the first 7 days postnatally, and continues to decrease, reaching the value seen for the adult rabbit by an age of 21 days. In contrast, the brain uptake of adenine is unusual in that there appears to be a very gradual reduction in brain uptake occurring throughout the suckling period. A 3-fold decrease in the BUI of choline was observed during the first 2 wk postpartum. Tryptophan uptake undergoes a 4-fold reduction in the first 4 wk postnatally . Only minor variations in the uptakes of glucose and butanol (a reference substance which is completely cleared by brain over a wide range of blood flow rates) were observed over the range of ages examined. Therefore modulations in adenine, arginine, choline, lactate and tryptophan permeability are not attributable to blood flow alterations.