Uptake of acetyl-l-carnitine in the brain

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Abstract
Analysis in mouse brain slices of the uptake of acetyl-l-[N-methyl-14C]carnitine with time showed it to be concentrative, and kinetic analysis gave aK m of 1.92 mM and aV max of 1.96 μmol/min per ml, indicating the presence of a low-affinity carrier system. The uptake was energy-requiring and sodium-dependent, being inhibited in the presence of nitrogen (absence of O2), sodium cyanide, low temperature (4°C), and ouabain, and in the absence of Na+. The uptake of acetyl-l-carnitine was not strictly substrate-specific; γ-butyrobetaine,l-carnitine,l-DABA, and GABA were potent inhibitors, hypotaurine andl-glutamate were moderate inhibitors, and glycine and β-alanine were only weakly inhibitory. In vivo, acetyl-l-carnitine transport across the blood-brain barrier had a brain uptake index of 2.4±0.2, which was similar to that of GABA. These results indicate an affinity of acetyl-l-carnitine to the GABA transport system.