Increase of tyrosine hydroxylase-like immunoreactive neurons in the nucleus accumbens and the olfactory bulb in the rat with the lesion in the ventral tegmental area of the midbrain

A small number of neurons in the nucleus accumbens of the rat showed tyrosine hydroxylase-like immunoreactivity (TH-LI). These TH-LI neurons had medium-sized cell bodies with several spiny dendrites. When a lesion was produced in the ventral tegmental area of the midbrain by injecting 6-hydroxydopamine, TH-LI neurons in the nucleus accumbens, as well as those in the olfactory bulb, were increased in number on the side ipsilateral to the lesion. The results indicated that expression of TH might be enhanced in some neurons deprived of dopaminergic afferent fibers.