Effect of aging on tyrosine hydroxylase protein content and the relative number of dopamine nerve terminals in human caudate

This study examined the effect of aging on the relative number of dopamine (DA) nerve terminals in human caudate nucleus, their content of tyrosine hydroxylase (TH) protein, and the relative abundance of TH monomers with different molecular weights. The results suggest that caudate TH levels plateau soon after birth and tend to remain relatively stable during aging, since no changes in either the relative number of TH-containing nerve terminals or the concentration of TH protein were found in subjects 15-63 years of age. The findings suggest that remaining DA neurons compensate to maintain caudate levels of TH protein and TH-containing nerve terminals.