The biological activity of many proteins, including voltage-sensitive ion channels, is controlled by their state of phosphorylation. Ca2+ influx through voltage-activated L-type Ca2+ channels serves as the major stimulatory signal in insulin-secreting cells. We have now investigated the extent to which Ca2+ handling in clonal insulin-secreting RiNm5F cells was affected by okadaic acid, an inhib...

Cardiac, skeletal, and smooth muscle cells shared the common feature of contraction in response to different stimuli. Agonist-induced muscle's contraction is triggered by a cytosolic free Ca2+ concentration increase due to a rapid Ca2+ release from intracellular stores and a transmembrane Ca2+ influx, mainly through L-type Ca2+ channels. Compelling evidences have demonstrated that Ca2+ might al...

Rapid inactivation of Ca2+ release-activated Ca2+ (CRAC) channels was studied in Jurkat leukemic T lymphocytes using whole-cell patch clamp recording and [Ca2+]i measurement techniques. In the presence of 22 mM extracellular Ca2+, the Ca2+ current declined with a biexponential time course (time constants of 8-30 ms and 50-150 ms) during hyperpolarizing pulses to potentials more negative than -4...

Whole-cell recordings and Ca2+ flux measurements were made at a giant calyx-type synapse in rat brainstem slices to determine the contribution of glutamate receptor (GluR) channels and voltage-dependent Ca2+ channels (VDCCs) to postsynaptic Ca2+ influx during synaptic transmission. A single presynaptic action potential (AP) evoked an EPSP, followed by a single AP. The EPSP-AP sequence caused a ...

We studied the magnitude and route(s) of Ca2+ flux from extra- to intracellular compartments during anoxia in adult rat optic nerve (RON), a central white matter tract, using Ca2+ sensitive microelectrodes to monitor extracellular [Ca2+] ([Ca2+]o). One hour of anoxia caused a rapid loss of the stimulus-evoked compound action potential (CAP), which partially recovered following re-oxygenation, i...

L-type Ca2+ channels select for Ca2+ over sodium Na+ by an affinity-based mechanism. The prevailing model of Ca2+ channel permeation describes a multi-ion pore that requires pore occupancy by at least two Ca2+ ions to generate a Ca2+ current. At [Ca2+] < 1 microM, Ca2+ channels conduct Na+. Due to the high affinity of the intrapore binding sites for Ca2+ relative to Na+, addition of microM conc...

The spatial arrangement of Ca2+ channels and vesicles remains unknown for most CNS synapses, despite of the crucial importance of this geometrical parameter for the Ca2+ control of transmitter release. At a large model synapse, the calyx of Held, transmitter release is controlled by several Ca2+ channels in a "domain overlap" mode, at least in young animals. To study the geometrical constraints...

The goal of this study was to examine the relationship between Ca2+ entry through L-type Ca2+ channels and local [Ca2+]i transients (Ca2+ sparks) in single rat cardiac ventricular cells. L-type Ca2+ channels were activated by depolarization of cell-attached membrane patches, and [Ca2+]i was measured simultaneously as fluo 3 fluorescence using laser scanning confocal microscopy. Patch depolariza...

We assessed the pathways by which excitatory and inhibitory neurotransmitters elicit postsynaptic changes in [Ca2+]i in brain slices of developing rat and cat neocortex, using fura 2. Glutamate, NMDA, and quisqualate transiently elevated [Ca2%]i in all neurons. While the quisqualate response relied exclusively on voltage-gated Ca2+ channels, almost all of the NMDA-induced Ca2+ influx was via th...

Within neurons, Ca2+-dependent inactivation (CDI) of voltage-gated L-type Ca2+ channels shapes cytoplasmic Ca2+ signals. CDI is initiated by Ca2+ binding to channel-associated calmodulin and subsequent Ca2+/calmodulin activation of the Ca2+-dependent phosphatase, calcineurin (CaN), which is targeted to L channels by the A-kinase-anchoring protein AKAP79/150. Here, we report that CDI of neuronal...