Effect of acetyl‐L‐carnitine on the dopaminergic system in aging brain

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Abstract
We studied the effect of acetyl‐L‐carnitine (ALCAR) on dopamine release and the effect of long‐term acetyl‐L‐carnitine treatment on age‐related changes in striatal dopamine receptors and brain amino acid levels. In striatal tissue that had been incubated with [3H]dopamine, acetyl‐L‐carnitine increased the release of [3H]dopamine evoked by electrical stimulation. In striatal tissue from aged mice administered acetyl‐L‐carnitine for 3 months, the release of [3H]dopamine evoked by electrical stimulation was higher than that of its aged control; the release after a second stimulation was similar in the two groups. There was a significant decline in the number of D1 striatal dopamine receptors with age. The Bmax was 51% lower in 1.5‐year‐old mice than in 4‐month‐old animals. Administration of acetyl‐L‐carnitine for 3 months diminished the reduction in the binding of [3H]SCH‐23390. [3H]Spiperonebinding to D2 receptors was not decreased with age and was not affected by acetyl‐L‐carnitine treatment. Age‐related decreases in levels of several amino acids were observed in several brain regions. Acetyl‐L‐carnitine lessened the reduction in the level of taurine only in the striatum. The findings confirm the multiple effects of acetyl‐L‐carnitine in brain, and suggest that its administration can have a positive effect on age‐related changes in the dopaminergic system.