Effect of exogenous L-dopa on behavior in the rat: an in vivo voltammetric study

Brain Res. 1989 Jun 26;490(2):332-8. doi: 10.1016/0006-8993(89)90250-3.

Abstract

L-DOPA was administered intraperitoneally (i.p.) or intraventricularly (i.v.t.) to freely moving rats to investigate the effects of exogenous L-DOPA itself on behavior. Striatal dopamine (DA) in the extracellular fluid was examined with microcomputer-controlled in vivo voltammetry, and behavioral change was observed. When L-DOPA was administered (i.p.) after pretreatment with benserazide, a peripheral DOPA decarboxylase inhibitor, behavioral change was elicited before the elevation in DA and suppressed before its reduction. After pretreatment with NSD-1015, a central DOPA decarboxylase inhibitor, behavioral change was also elicited, although DA was still not increased. When L-DOPA was injected (i.v.t.), the behavioral effect was manifested at once; DA was still unchanged at this time, but it increased after behavioral activity reached the maximum level. L-DOPA was also injected (i.v.t.) into rats with striatal lesions induced by 6-hydroxydopamine (i.v.t.). Behavioral change was manifested promptly after the injection. When the dose-response curves to different dosages of L-DOPA were examined in normal rats without striatal lesions, it was found to exhibit a steeper rise than that of DA. Finally, when rats were injected (i.p. or i.v.t.) with 3-O-methyl-DOPA (3-methoxytyrosine), a major metabolite of L-DOPA, no behavioral change was elicited, and no increase in DA was recognized. These experimental results indicated that L-DOPA is related directly to the manifestation of behavioral change.

MeSH terms

  • 3,4-Dihydroxyphenylacetic Acid / metabolism
  • Animals
  • Behavior, Animal / drug effects*
  • Corpus Striatum / drug effects
  • Corpus Striatum / metabolism
  • Corpus Striatum / physiology*
  • Dopamine / metabolism
  • Dose-Response Relationship, Drug
  • Electrochemistry
  • Injections, Intraperitoneal
  • Injections, Intraventricular
  • Levodopa / administration & dosage
  • Levodopa / pharmacology*
  • Male
  • Rats
  • Rats, Inbred Strains

Substances

  • 3,4-Dihydroxyphenylacetic Acid
  • Levodopa
  • Dopamine