Dopamine depletion in nigrostriatal neurons in the genetically diabetic rat

Employing tyrosine hydroxylase (TH) immunohistochemistry, we have revealed that the enzyme is depleted in nigrostriatal neurons in the genetically diabetic BB Wistar (BBWd) rat. A similar, but much less marked reduction in TH immunoreactivity occurred in the mesolimbic dopamine system, which arises from the ventral tegmental area and terminates in the nucleus accumbens. The projection to the olfactory tubercle appeared unaffected. Since the decreased levels of dopamine in the mesencephalic dopamine systems could not be restored under insulin-controlled conditions, the impairment of dopamine biosynthesis in the BBWd rat may be genetically programmed.