Effect of an homologous series of aliphatic alcohols on neuronal and smooth muscle voltage-dependent Ca2+ channels.

The acute inhibitory actions of alcohol on K(+)-stimulated 45Ca2+ uptake into synaptosomes shows regional variation in sensitivity throughout the brain, suggesting the possibility of a selective action on a specific Ca2+ channel subtype. This was examined by comparing the effects of a homologous series of aliphatic alcohols on synaptosomal Ca2+ channels with their actions on K(+)-stimulated Ca2+ channels in guinea-pig intestinal longitudinal muscle, which have been demonstrated to be of the L-type. K(+)-stimulated contraction of and [3H]nitrendipine binding to smooth muscle were both inhibited by the alcohols at similar concentrations, with the potency increasing with chain length.

1,4-Dihydropyridine activators in the tiamdipine series.

The pharmacologic and radioligand binding properties of 5-nitro analogs of the 1,4-dihydropyridine Ca2+ channel antagonist, tiamdipine (2-(2-aminoethylthio)methyl-3-carbomethoxy-5-carbomethoxy-6-m ethyl-4-(3-nitrophenyl)-1,4-dihydropyridine) and its N-formyl derivative have been measured in rat tail artery, guinea pig ileum and rat heart. The enantiomers of both analogs showed activator and antagonist properties, the latter being exhibited at lower concentrations.

Characterization of ion movements and their relationship to muscarinic receptor binding and excitation-contraction coupling in guinea pig ileal longitudinal smooth muscle.

The relationship between ion movements (sodium uptake and potassium release) and agonist-induced contractile responses or muscarinic receptor binding was investigated in the guinea pig ileal longitudinal muscle (GPLM). Sodium uptake and potassium release were agonist-dependent, concentration-dependent, and stereoselective, with the following rank order of maximum ion movement: muscarinic agonists greater than histamine greater than substance P = serotonin. Potassium depolarization did not initiate sodium uptake or potassium release.

Binding of A 1,4-dihydropyridine calcium channel activator, (-) S Bay K 8644, to cardiac preparations.

The 1,4-dihydropyridine Ca2+ channel activator, (-) [3H]Bay K 8644, binds to cardiac membranes and polarized [5 mM K+] and depolarized [50 mM K+] cardiac cells. Binding to microsomal membranes at 25 degrees C indicates a single set of binding sites, KD = 2.9 x 10(-9) M and a site density, 337 fmoles/mg protein, not different from that measured by antagonist 1,4-dihydropyridines.