Specific high-affinity binding sites for [3H]Ro 5-4864 in rat brain and kidney

J Pharmacol Exp Ther. 1983 Apr;225(1):61-9.


The binding of the novel ligand [3H]Ro 5-4864 to membrane preparations of rat kidney and brain was studied. [3H]Ro 5-4864 binds with high affinity (Kd = 0.6 nM) to a single saturable population of benzodiazepine recognition sites on renal membranes. Binding is rapidly reversible and, based on its pharmacological spectrum, takes place at the peripheral-type, Ro 5-4864-sensitive receptor. Specific high-affinity (Kd = 1.1 nM) [3H] Ro 5-4864 binding to the peripheral-type benzodiazepine binding site can also be demonstrated using rat brain membranes. [3H] Ro 5-4864 lacks stereospecificity with regard to chiral activity in position 3. A comparison of benzodiazepine inhibitory potency and structural features reveals that whereas a 4'-substitution assures specificity for the peripheral-type receptor, an N-methyl moiety is essential for optimal activity. [3H]Ro 5-4864 binding to brain membranes is temperature sensitive and is not modulated by barbiturates, convulsants, gamma-aminobutyric acid and chloride anions. The pyrazolopyridine derivative tracazolate inhibits [3H] Ro 5-4864 binding. The regional and subcellular distribution of binding is distinctly different from that previously demonstrated for [3H]benzodiazepine binding in the brain. The olfactory bulb shows the highest binding density, whereas the cerebral cortical, striatal and hippocampal areas are lowest among those areas studied. In the brain, [3H]Ro 5-4864 binding was found to sediment with the nuclear fraction. In conclusion, the present study shows that [3H]Ro 5-4864 is a selective ligand of the peripheral-type benzodiazepine binding site that can unequivocally be demonstrated in the kidney as well as the brain. The physiological significance of these findings, however, remain to be established.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Anti-Anxiety Agents / pharmacology
  • Benzodiazepinones / metabolism*
  • Binding, Competitive
  • Brain / metabolism*
  • Cerebral Cortex / metabolism
  • Chlorides / pharmacology
  • Kidney / metabolism*
  • Kinetics
  • Male
  • Olfactory Bulb / metabolism
  • Rats
  • Rats, Inbred Strains
  • Receptors, Cell Surface / analysis*
  • Receptors, GABA-A
  • Subcellular Fractions / metabolism
  • Temperature


  • Anti-Anxiety Agents
  • Benzodiazepinones
  • Chlorides
  • Receptors, Cell Surface
  • Receptors, GABA-A
  • 4'-chlorodiazepam