Non-serine-phosphorylated tyrosine hydroxylase expressing neurons are present in mouse striatum, accumbens and cortex that increase in number following dopaminergic denervation.

ABSTRACT

Neurons partially expressing individual enzymes of dopamine (DA) biosynthesis, e.g. tyrosine hydroxylase (TH) or aromatic acid decarboxylase, are found in different areas of the central nervous system, continuously or transiently in normal and pathological conditions. This current study analyzed if TH neurons exist in target areas of ventral midbrain dopaminergic neurons and how they react to dopaminergic denervation. High power analysis of brain tissue sections revealed that TH-immunopositive neurons were present in striatum, accumbens and cortex - and several other brain areas - of healthy adult mice. DAergic denervation induced by stereotaxic injection of 6-hydroxydopamine into the medial forebrain bundle increased the number of TH expressing neurons in the striatum, accumbens and the cortex, up 40 d later. These TH neurons were not stained by specific antibodies recognizing TH phosphorylated at serine residues 19, 31 and 40, dopamine transporter and vesicular monoamine transporter type 2, but most of them expressed dopamine and cyclic AMP-regulated phosphoprotein 32kDa. Thus, mouse striatum, accumbens and cortex contain neurons which express TH with low activity, and their number increases following dopamine depletion.