Transgene expression within the spinal cord of hTH-eGFP rats.

The enzyme tyrosine hydroxylase (TH) is broadly expressed in catecholaminergic neurons. In the spinal cord, four components contain TH, including A11 diencephalospinal dopaminergic (DA-ergic) pathways, intraspinal DA-related neurons, supraspinal noradrenergic projections, and afferents of TH-expressing sensory neurons. A human TH-enhanced green fluorescent protein (hTH-eGFP) transgenic rat was recently developed to tag TH+ profiles in the nervous system for visualization. Using immunostaining, we found that only A11 pathways express GFP whereas the other 3 components do not in the spinal cord. Thus, this may suggest a genetic difference among these TH+ elements even though they produce the same protein.