Identification and characterisation of 5-hydroxytryptamine 3 recognition sites in human brain tissue

J M Barnes, N M Barnes, B Costall, J W Ironside, R J Naylor

Research output: Contribution to journalArticlepeer-review


[3H]Zacopride displayed regional saturable specific binding to homogenates of human brain tissues, as defined by the inclusion of BRL43694 [endo-N-(9-methyl-9-azabicyclo[3.3.1]non-3-yl)-1-methylindazole-3- carboxamide] in the incubation media. Scatchard analysis of the saturation data obtained from amygdaloid and hippocampal tissues identified the binding as being of high affinity and to a homogeneous population of binding sites (KD = 2.64 +/- 0.75 and 2.93 +/- 0.41 nmol/L and Bmax = 55 +/- 7 and 44 +/- 9 fmol/mg of protein in the amygdala and hippocampus, respectively). 5-Hydroxytryptamine 3 (5-HT3) receptor agonists and antagonists competed for the [3H]zacopride binding site, competing with up to 40% of total binding with a similar rank order of affinity in both tissues; agents acting on various other neurotransmitter receptors failed to inhibit binding. Kinetic data revealed a fast association that was fully reversible (k+1 = 6.61 X 10(5) and 7.65 X 10(5)/mol/L/s and k-1 = 3.68 X 10(-3) and 3.45 X 10(-3)/s in the amygdala and hippocampus, respectively). It is concluded that [3H]zacopride selectively labels with high affinity 5-HT3 recognition sites in human amygdala and hippocampus and, if these binding domains represent 5-HT3 receptors, may provide the opportunity for 5-HT3 receptor antagonists to modify 5-HT function in the human brain.

Original languageEnglish
Pages (from-to)1787-93
Number of pages7
JournalJournal of Neurochemistry
Issue number6
Publication statusPublished - Dec 1989


  • Adult
  • Aged
  • Amygdala
  • Benzamides
  • Bicyclo Compounds
  • Bicyclo Compounds, Heterocyclic
  • Binding, Competitive
  • Brain
  • Hippocampus
  • Humans
  • Kinetics
  • Male
  • Middle Aged
  • Receptors, Serotonin
  • Serotonin Antagonists
  • Tritium


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