Characterisation and autoradiographic localisation of 5-HT3 receptor recognition sites identified with [3H]-(S)-zacopride in the forebrain of the rat

Neuropharmacology. 1990 Nov;29(11):1037-45. doi: 10.1016/0028-3908(90)90110-d.


The pharmacological characterisation and topographical distribution of [3H]-(S)-zacopride recognition sites in the forebrain of the rat was studied using homogenate and autoradiographic radioligand binding techniques. [3H]-(S)-Zacopride labelled a single, saturable, specific binding site (defined by 10.0 microM granisetron) in homogenates prepared from the entorhinal cortex of the rat (pKD = 9.51 +/- 0.08; Bmax = 104 +/- 7 fmol mg-1 protein; mean +/- SEM, n = 8). Pharmacological characterisation of the recognition site, within the entorhinal cortex, suggested that [3H]-(S)-zacopride selectively labelled the recognition site of the 5-HT3 receptor. Specific binding of [3H]-(S)-zacopride (defined by 1.0 microM granisetron) was differentially distributed throughout the forebrain of the rat; highest densities were located within sub-nuclei of the amygdala (cortical amygdaloid nucleus, amygdalohippocampal area, posterior medial cortical amygdaloid nucleus, posterior lateral amygdaloid nucleus), cortical areas (primary olfactory cortex, entorhinal cortex) and hippocampus. Non-specific binding was distributed homogeneously, although lower in myelinated structures. It is concluded that [3H]-(S)-zacopride selectively labels 5-HT3 receptor recognition sites within the forebrain of the rat; the topographical distribution of these sites, within the limbic nuclei, is consistent with the behavioural actions in animal models of the selective 5-HT3 receptor antagonists.

MeSH terms

  • Animals
  • Autoradiography
  • Benzamides / metabolism*
  • Binding, Competitive
  • Brain / metabolism*
  • Bridged Bicyclo Compounds / metabolism*
  • Bridged Bicyclo Compounds, Heterocyclic*
  • Female
  • Hippocampus / metabolism
  • Kinetics
  • Organ Specificity
  • Rats
  • Rats, Inbred Strains
  • Receptors, Serotonin / metabolism*
  • Serotonin Antagonists / metabolism*
  • Tritium


  • Benzamides
  • Bridged Bicyclo Compounds
  • Bridged Bicyclo Compounds, Heterocyclic
  • Receptors, Serotonin
  • Serotonin Antagonists
  • Tritium
  • zacopride