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

Abstract

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.

• Authors: S C Lummis, M I Sepúlveda, G J Kilpatrick, J Baker
• Journal: European journal of pharmacology (Eur J Pharmacol) Vol. 243 Issue 1 Pg. 7-11 (Oct 12 1993) ISSN: 0014-2999 [Print] Netherlands
• PMID: 8253126 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

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

Topics

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