Dopaminergic characterization in LRRK2 KO mice. (a,b) Unbiased sterological estimates for TH-positive (a) neurons and (b) dendrites in the substantia nigra reveal no difference between WT and LRRK2 KO mice. Counting was performed using optical fractionator probes in TH stained sections from 18 month old WT and KO mice. (c-e) Dopamine axon terminal neurochemistry is normal in LRRK2 KO mice. HPLC analysis of total striatal content of dopamine (da) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). (f-g) Mean of individual animal turnover ratios of DA to metabolites DOPAC and HVA. (h-i) In vivo microdialysis reveals similar baseline and KCl-evoked levels of extracellular DA in WT, HET and KO mice (i). DA levels were plotted as a percentage of each individual animal’s mean baseline levels to compare response over time (h)% Response did not differ between WT, HET and KO mice. Dopamine levels were measured by HPLC from dialysates collected from the striatum. All data are presented as mean ± SEM.