Characterization of a Novel 5-HT4 Receptor Antagonist of the Azabicycloalkyl Benzimidazolone Class: DAU 6285

Naunyn Schmiedebergs Arch Pharmacol. 1992 Mar;345(3):264-9. doi: 10.1007/BF00168685.

Abstract

Three chemical classes of serotonin 5-HT4 receptor agonists have been identified so far: 5-substituted indoles (e.g. 5-HT), benzamides (e.g. renzapride) and benzimidazolones (e.g. BIMU 8). In a search for 5-HT4 receptor antagonists, we have discovered that the benzimidazolone derivative DAU 6285 (for structure see text), is 3-5 times more potent than tropisetron in blocking 5-HT, renzapride and BIMU 8 induced stimulation of adenylate cyclase activity in mouse embryo colliculi neurons. Schild plot analysis yielded Ki values of 220, 181 and 255 nmol/l, respectively. In addition, DAU 6285 showed poor activity as a 5-HT3 receptor ligand with respect to tropisetron, as demonstrated by in vitro binding studies (Ki, 322 vs 2.8 nmol/l) and by its antagonistic activity in the Bezold-Jarisch reflex test (ID50, 231 vs 0.5 micrograms/kg, i.v.). No significant binding (Ki greater than 10 mumol/l) of DAU 6285 to serotonergic 5-HT1A, 5-HT1B, 5-HT1C, 5-HT1D, and 5-HT2 receptors as well as to adrenergic alpha 1, alpha 2, dopaminergic D1, D2 or muscarinic M1-M3 receptor subtypes was found. The data indicate that DAU 6285 has a somewhat higher affinity than tropisetron for 5-HT4 receptors, a property confirmed in functional tests, and much lower affinity than tropisetron for 5-HT3 receptors. The compound represents a new interesting tool for investigating the pharmacological and physiological properties of 5-HT4 receptors.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Benzamides / pharmacology
  • Benzimidazoles / pharmacology*
  • Brain / cytology
  • Brain / ultrastructure
  • Bridged Bicyclo Compounds / pharmacology*
  • Bridged Bicyclo Compounds, Heterocyclic*
  • Cells, Cultured
  • Cyclic AMP / biosynthesis
  • Embryo, Mammalian
  • Heart Rate / drug effects
  • Indoles / pharmacology
  • Kinetics
  • Mesencephalon / cytology
  • Mesencephalon / ultrastructure
  • Mice
  • Rats
  • Receptors, Serotonin / classification
  • Receptors, Serotonin / metabolism
  • Reflex / drug effects
  • Serotonin / pharmacology
  • Serotonin Antagonists* / pharmacology
  • Stimulation, Chemical
  • Tropisetron

Substances

  • Benzamides
  • Benzimidazoles
  • Bridged Bicyclo Compounds
  • Bridged Bicyclo Compounds, Heterocyclic
  • Indoles
  • Receptors, Serotonin
  • Serotonin Antagonists
  • DAU 6285
  • (endo-N-8-methyl-8-azabicyclo-(3.2.1)oct-3-yl)-2,3-dihydro-3-isopropyl-2-oxo-1H-benzimidazol-1-carboxamide
  • Serotonin
  • Tropisetron
  • renzapride
  • Cyclic AMP