(-)-[3H] desmethoxyverapamil labels multiple calcium channel modulator receptors in brain and skeletal muscle membranes: differentiation by temperature and dihydropyridines

J Pharmacol Exp Ther. 1986 Jun;237(3):731-8.


The verapamil-like calcium channel modulator, (-)-[3H]desmethoxyverapamil binds to multiple sites in microsomal membrane preparations from brain and skeletal muscle. In brain the Kd values of the sites are 0.55 +/- 0.1 and 61.8 +/- 18 nM for the high and low affinity sites and the maximum binding values are 0.22 +/- 0.04 and 4.6 +/- 1.0 pmol/mg of protein, respectively. Equilibrium analysis of saturation data in skeletal muscle membranes shows only one site with an affinity of 7.2 +/- 0.8 nM and a maximum binding of 2.96 +/- 0.32 pmol/mg of protein. However, a low affinity site with an estimated Kd of 152 nM is indicated in dissociation kinetic studies. Dihydropyridine calcium channel modulators regulate the binding of desmethoxyverapamil in a temperature-dependent fashion with (+)-PN 200110 decreasing (-)-[3H]desmethoxyverapamil binding more at 0 degrees C than at higher temperatures and, at 37 degrees C, enhancing binding in skeletal muscle. The influence of (+)-desmethoxyverapamil on (+)-[3H]PN 200110 binding is unchanged by temperature variations, whereas interactions of the (-)-enantiomer are altered markedly with more inhibition at 0 degrees C than at higher temperatures and, in skeletal muscle, stimulation of binding at 37 degrees C. Dissociation studies indicate that the two sites labeled by (-)-[3H]-desmethoxyverapamil in skeletal muscle interact in a negative heterotropic cooperative fashion. Dihydropyridines appear to slow the dissociation of ligand from the low affinity site, whereas diltiazem accelerates the dissociation of (-)-[3H]desmethoxyverapamil from the high affinity site. These results suggest that the high and low affinity sites labeled by (-)-[3H]desmethoxyverapamil, respectively, represent the verapamil and diltiazem receptors in brain and skeletal muscle.

Publication types

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

MeSH terms

  • Animals
  • Brain Chemistry*
  • Calcium / pharmacology
  • Calcium Channels
  • Cell Membrane / analysis
  • Dihydropyridines*
  • Female
  • Isradipine
  • Kinetics
  • Male
  • Muscles / analysis*
  • Oxadiazoles / metabolism
  • Pyridines / metabolism
  • Pyridines / pharmacology*
  • Rabbits
  • Receptors, Nicotinic / analysis*
  • Receptors, Nicotinic / metabolism
  • Stereoisomerism
  • Temperature*
  • Tritium
  • Verapamil / analogs & derivatives*
  • Verapamil / metabolism


  • Calcium Channels
  • Dihydropyridines
  • Oxadiazoles
  • Pyridines
  • Receptors, Nicotinic
  • Tritium
  • 1,4-dihydropyridine
  • 4-desmethoxyverapamil
  • Verapamil
  • Calcium
  • Isradipine