Binding of the cage convulsant, [3H]TBOB, to sites linked to the GABAA receptor complex

Eur J Pharmacol. 1990 Apr 25;179(3):419-25. doi: 10.1016/0014-2999(90)90183-7.


[3H]t-Butylbicycloorthobenzoate ([3H]TBOB) binds to specific sites on crude synaptic rat brain membranes. The dissociation constant, Kd, determined from saturation experiments is near 8 nM and the receptor density Bmax is about 20 pmol/g wet tissue. Non-specific binding constitutes about 35% of the total binding at 4 nM [3H]TBOB. The association of [3H]TBOB is monophasic but its dissociation is biphasic. Kd values of 8 nM (70% of the binding sites) and 20 nM (30% of the binding sites) were estimated from the kinetic data. These values differ from those previously reported. Specifically bound [3H]TBOB is displaced by picrotoxin and by t-butylbicyclophosphorothionate (TBPS). No simple competitive interaction of picrotoxin with [3H]TBOB binding was found. Micromolar quantities of the GABAergic facilitating compounds, GABA, muscimol and diazepam inhibited [3H]TBOB binding in an allosteric manner.

MeSH terms

  • Animals
  • Binding, Competitive
  • Bridged Bicyclo Compounds / metabolism*
  • Bridged Bicyclo Compounds, Heterocyclic*
  • Bridged-Ring Compounds / metabolism*
  • In Vitro Techniques
  • Kinetics
  • Male
  • Membranes / metabolism
  • Picrotoxin / metabolism
  • Rats
  • Rats, Inbred Strains
  • Receptors, GABA-A / metabolism*
  • Synapses / metabolism


  • Bridged Bicyclo Compounds
  • Bridged Bicyclo Compounds, Heterocyclic
  • Bridged-Ring Compounds
  • Receptors, GABA-A
  • Picrotoxin
  • tert-butylbicyclo-2-benzoate