Differential effects of L-trytophan and buspirone on biogenic amine contents and metabolism in Lurcher mice cerebellum.

The effects of serotoninergic stimulation on monoamines were studied in the heterozygous Lurcher (Lc/+) mutant mouse, a model of human cerebellar ataxia. Wild type (+/+) and Lc/+ mice were treated for 40 days with L-tryptophan or buspirone, and serotonin (5-HT), dopamine (DA), noradrenaline (NA) and their main metabolites were measured in the cerebellum. In +/+ mice, only buspirone increased concentrations of 5-HT metabolites. In the hypoplastic Lc/+ cerebellum, indoleamines were higher, and increased further after both treatments. The 5-HT turnover index was increased in +/+ mice by buspirone, while in Lc/+ mutants it increased after L-tryptophan but was decreased by buspirone, indicating that in the mutants nerve terminals synthesize and accumulate 5-HT, but may not utilize it efficiently. Catecholamine contents remained unchanged in +/+ mice, but in Lc/+ mutants with higher endogenous NA, L-tryptophan further increased NA and 3,4-dihydroxy-phenylacetic acid (DOPAC), and buspirone augmented NA, DA and DOPAC levels.