Increase in mouse brain regional noradrenaline turnover after L-dopa administration

Noradrenaline (NA) and its major metabolite, 3-methyl-4-hydroxyphenylethylene glycol (MHPG) were measured by HPLC with electrochemical detection in five mouse brain regions after L-dopa treatment. Noradrenaline concentration increased significantly, by 30-40%, in the three terminal regions of the locus coeruleus; cortex, hippocampus and cerebellum, but did not change in hypothalamus and brainstem. In mice whose central NA levels had been depleted by prior treatment with the neurotoxin, DSP-4, remaining NA neurons in these terminal regions were still able to respond with an increase in NA after L-dopa loading. The NA metabolite, MHPG, increased several-fold in all five regions in both saline and DSP-4-pretreated mice. Thus, L-dopa may be a useful precursor of NA in specific brain regions, particularly when NA is depleted.