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Multiple [3H]-nemonapride binding sites in calf brain

  • D. M. Helmeste
  • S. W. Tang
  • Ming Li
  • Hong Fang
Original article

Abstract

[3H]-Nemonapride has been the ligand of choice to label D4 dopamine receptors. Its specificity was questioned when it was discovered that sigma (σ) sites were also labeled by [3H]-nemonapride. To further characterize the binding of [3H]-nemonapride, three areas of calf brain (striatum, frontal cortex and cerebellum) were examined. In all three areas, [3H]-nemonapride labeled multiple sites. Dopaminergic and σ sites were the most prominent. The σ binding profile was σ-1 like with a Ki binding profile as follows (in order of decreasing potency): haloperidol, PPAP, pentazocine, DTG, U-50488, R(+)-3-PPP. Experiments using sulpiride and pentazocine to block striatal dopaminergic and σ sites, respectively, revealed additional, not previously characterized binding sites for [3H]-nemonapride. One component which was present in striatum but not in frontal cortex or cerebellum, had affinity for some neuroleptics and WB-4101, but not for typical serotonergic agents. Thus, [3H]-nemonapride has no selectivity for dopamine receptors unless stringent experimental conditions are met.

Key words Dopamine receptors Sigma receptors Serotonin receptors 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • D. M. Helmeste
    • 1
  • S. W. Tang
    • 1
  • Ming Li
    • 1
  • Hong Fang
    • 1
  1. 1.Department of Psychiatry and Human Behavior, University of California, Irvine, Irvine, CA 92697-1681, USAUS

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