Chronic L-DOPA treatment differentially regulates gene expression of glutamate decarboxylase, preproenkephalin and preprotachykinin in the striatum of 6-hydroxydopamine-lesioned rat

Neuroscience. 1995 May;66(1):19-28. doi: 10.1016/0306-4522(94)00574-o.


The effect of a unilateral 6-hydroxydopamine lesion of the medial forebrain bundle in rats and subsequent L-DOPA treatment for eight weeks on preproenkephalin, preprotachykinin and glutamate decarboxylase (M(r) 67,000) gene expression in the striatum was investigated by in situ hybridization. A 6-hydroxydopamine lesion of the medial forebrain bundle markedly increased the level of preproenkephalin messenger RNA (+66%) and modestly elevated the level of glutamate decarboxylase (M(r) 67,000) messenger RNA (+36%) in the denervated striatum, but caused a decrease in the level of preprotachykinin messenger RNA (-54%) relative to the intact striatum and to sham-lesioned control animals. Treatment with L-DOPA (200 mg/kg/24 h) for eight weeks reduced but did not abolish the 6-hydroxydopamine lesion-induced elevation of preproenkephalin messenger RNA and slightly reduced the elevation of glutamate decarboxylase (M(r) 67,000) messenger RNA in denervated striatum relative to intact side and control groups. However, L-DOPA treatment almost completely reversed the decrease in preprotachykinin messenger RNA caused by 6-hydroxydopamine lesioning when compared to intact side and control groups. The effect of L-DOPA on the gene expression of preproenkephalin and glutamate decarboxylase (M(r) 67,000) differs from the increase in striatal enkephalin content and glutamate decarboxylase activity previously found following L-DOPA treatment. In contrast, L-DOPA reversed the changes in preprotachykinin messenger RNA, reflecting previously reported increases in substance P content. The findings provide new evidence that chronic L-DOPA treatment differentially affects direct striatonigral and indirect striatopallidal pathways at the molecular level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Behavior, Animal / drug effects
  • Carbidopa / pharmacology
  • Enkephalins / biosynthesis*
  • Female
  • Gene Expression Regulation, Enzymologic / drug effects*
  • Glutamate Decarboxylase / biosynthesis*
  • In Situ Hybridization
  • Levodopa / pharmacology*
  • Molecular Sequence Data
  • Neostriatum / anatomy & histology
  • Neostriatum / drug effects
  • Neostriatum / metabolism*
  • Oligonucleotide Probes
  • Oxidopamine / pharmacology*
  • Protein Precursors / biosynthesis*
  • RNA, Messenger / biosynthesis
  • Rats
  • Rats, Wistar
  • Tachykinins / biosynthesis*


  • Enkephalins
  • Oligonucleotide Probes
  • Protein Precursors
  • RNA, Messenger
  • Tachykinins
  • preprotachykinin
  • Levodopa
  • Oxidopamine
  • preproenkephalin
  • Glutamate Decarboxylase
  • Carbidopa