Changes in Neostriatal Dopamine Concentrations in Response to Levodopa Infusions

Changes in Neostriatal Dopamine Concentrations in Response to Levodopa Infusions Abstract: Levodopa was infused under various circumstances of pretreatment into the ear veins of unanesthetized rabbits. Concentrations of neostriatal dopamine formed in response to levodopa administration were determined. The aim was to characterize the temporal relationship between the concentrations of levodopa in plasma and dopamine in the neostriatum. When plasma levodopa was maintained constant by i.v. infusion, the concentration of neostriatal dopamine reached a plateau by 1 h. Increases in dopamine were proportional to the amount of precursor in plasma. The tissue half‐life of this dopamine in normal rabbits was not more than 15 min. Half‐lives of comparable duration for striatal dopamine were calculated from rabbits treated chronically with levodopa, and from rabbits with monoamine‐depleting lesions. The results show that the concentration of dopamine in rabbit neostriatum correlates closely with the concentration of levodopa in plasma. Concurrent analyses of neocortical tissues indicate that the neostriatum may not be different from other brain regions with regard to dopamine storage mechanisms. Interpretation of the results in terms of the clinical use of levodopa suggests that the durations of short‐term effects (measured in h) of the drugs are paralleled by changes in concentration of brain dopamine. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neurochemistry Wiley

Changes in Neostriatal Dopamine Concentrations in Response to Levodopa Infusions

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Publisher
Wiley
Copyright
Copyright © 1980 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0022-3042
eISSN
1471-4159
DOI
10.1111/j.1471-4159.1980.tb09969.x
Publisher site
See Article on Publisher Site

Abstract

Abstract: Levodopa was infused under various circumstances of pretreatment into the ear veins of unanesthetized rabbits. Concentrations of neostriatal dopamine formed in response to levodopa administration were determined. The aim was to characterize the temporal relationship between the concentrations of levodopa in plasma and dopamine in the neostriatum. When plasma levodopa was maintained constant by i.v. infusion, the concentration of neostriatal dopamine reached a plateau by 1 h. Increases in dopamine were proportional to the amount of precursor in plasma. The tissue half‐life of this dopamine in normal rabbits was not more than 15 min. Half‐lives of comparable duration for striatal dopamine were calculated from rabbits treated chronically with levodopa, and from rabbits with monoamine‐depleting lesions. The results show that the concentration of dopamine in rabbit neostriatum correlates closely with the concentration of levodopa in plasma. Concurrent analyses of neocortical tissues indicate that the neostriatum may not be different from other brain regions with regard to dopamine storage mechanisms. Interpretation of the results in terms of the clinical use of levodopa suggests that the durations of short‐term effects (measured in h) of the drugs are paralleled by changes in concentration of brain dopamine.

Journal

Journal of NeurochemistryWiley

Published: May 1, 1980

References

  • Dynamic characteristic of the functional compartment of dopamine in dopaminergic terminals of the rat striatum
    Javoy, Javoy; Glowinski, Glowinski
  • Metabolism of levodopa in the human brain
    Lloyd, Lloyd; Davidson, Davidson; Hornykiewicz, Hornykiewicz

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