[(3)H]Nitrendipine, a potent calcium channel antagonist [3-ethyl-5-methyl-1-1,4-dihydro-2,6 - dimethyl - 4 - (3 - nitrophenyl) - 3,5 - pyridine carboxylate], was used to label high affinity binding sites on membranes prepared from bovine aortic smooth muscle. The binding of [(3)H]nitrendipine is rapid (t(1/2) < 5 min) and reversible at 37 degrees C. The binding sites have a high affinity for [(...

Mice were rendered tolerant and dependent to morphine by subcutaneous injection of morphine over a period of 5 days. The effects of acute and chronic administration of dihydropyridine calcium channel antagonist nifedipine on the development of tolerance and naloxone-precipitated morphine withdrawal signs were investigated. A single injection of nifedipine proved to be effective in inhibiti...

in this study, the possible involvement of l-type voltage-operated calcium channels in the vasorelaxant effect of the flavonoid quercetin was investigated, using the isolated aortic rings from normal male rats. addition of quercetin (0.1 µm-1 mm) caused a significant dose-dependent relaxation of noradrenaline (na)- and kcl-preconstricted rings and nifedipine attenuated this response, especially...

mice were rendered tolerant and dependent to morphine by subcutaneous injection of morphine over a period of 5 days. the effects of acute and chronic administration of dihydropyridine calcium channel antagonist nifedipine on the development of tolerance and naloxone-precipitated morphine withdrawal signs were investigated. a single injection of nifedipine proved to be effective in inhibiting so...

To determine whether calcium channel agonists and antagonists bind to distinct pharmacologically active sites, the binding of dihydropyridine calcium channel agonists and antagonists was related to calcium flux and contractile state in primary monolayer cultures of spontaneously contracting chick embryo ventricular cells. Equilibrium binding studies using the antagonist (+)-[3H]PN200-110 demons...

A long-standing question in neurobiology is whether astrocytes respond to the neuronal release of neurotransmitters in vivo. To address this question, acutely isolated hippocampal slices were loaded with the calcium-sensitive dye Calcium Green-1 and the responses of the astrocytes to electrical stimulation of the Schaffer collaterals were monitored by confocal microscopy. To confirm that the re...

A protein that imitates the sequence of a highly conserved segment predicted to line the pore of dihydropyridine-sensitive L-type calcium channels was designed and synthesized. Single-channel conductance properties were studied in planar lipid bilayers. The synthetic protein emulates the ionic conductance, ionic selectivity, and pharmacological properties of the authentic calcium channel, inclu...