Characterization of [3H]meta-chlorophenylbiguanide binding to 5-HT3 receptors in N1E-115 neuroblastoma cells

Eur J Pharmacol. 1993 Oct 12;243(1):7-11. doi: 10.1016/0014-2999(93)90160-j.


The binding characteristics of a radiolabelled 5-HT3 receptor agonist, [3H]meta-chlorophenylbiguanide (mCPBG), were examined in membranes from N1E-115 neuroblastoma cells. Scatchard plots of saturation binding data showed the presence of two populations of binding sites, with Kd = 0.03 +/- 0.01 nM and 4.4 +/- 1.2 nM and Bmax = 11.9 +/- 4.2 and 897.9 +/- 184.7 fmol/mg protein respectively. Competition studies with a selection of agonists and antagonists revealed the pharmacological profile expected for a 5-HT3 receptor. The rank order of potency for antagonists was granisetron > quipazine > GR65630 > ondansetron > MDL72222, and for agonists was mCPBG > 5-HT (5-hydroxytryptamine, serotonin) > 2-methyl-5-HT. IC50 values for 5-HT and 2-methyl-5-HT were lower than those observed using radiolabelled antagonists, and combined with functional experiments, the data suggest that [3H]mCPBG may label high affinity desensitized states of the receptor. We conclude that [3H]mCPBG labels 5-HT3 receptors in N1E-115 neuroblastoma cell membranes and may be a useful compound with which to explore 5-HT3 receptors in other systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biguanides / metabolism*
  • Binding, Competitive
  • Electrophysiology
  • Mice
  • Neuroblastoma / metabolism*
  • Radioligand Assay
  • Receptors, Serotonin / metabolism*
  • Tritium
  • Tumor Cells, Cultured


  • Biguanides
  • Receptors, Serotonin
  • Tritium
  • 1-(3-chlorophenyl)biguanide