TH MESSENGER-RNA OVER-EXPRESSION IN RATS WITH CHRONIC EXCITOTOXIC STRIATAL LESIONS

TWENTY weeks after ibotenic acid lesions of the striatum, the amount o f tyrosine hydroxylase (TH) in this structure was markedly increased. This was accompanied by a 3-fold increase in TH mRNA levels in the ips ilateral subtantia nigra (SN). Striatal levels of dopamine (DA) and di hydroxyphenylacetic acid (DOPAC) were markedly reduced. In the nucleus accumbens, spared by the lesion, DA neurotransmission was also altere d, as evidenced by a reduction of DA and DOPAC, but no increase in TH could be detected. TH mRNA levels were moderately enhanced in the vent ral tegmental area (VTA). Thus, lesioning in the striatum induces TH g ene activation in both SN and VTA neurones, not strictly related to DA function at the terminal level.