Pancreatic beta-cells and HIT-T15 cells exhibit oscillations of cytosolic calcium ([Ca2+]i) that are dependent on glucose metabolism and appear to trigger pulsatile insulin secretion. Significantly, differences in the pattern of this [Ca2+]i oscillatory activity may have important implications for our understanding of how glucose homeostasis is achieved during the feeding and fasting states. Wh...

Adenophostin-A, a novel compound isolated from cultures of Penicillium brevicompactum, has been shown to stimulate Ca2+ release from inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ stores in microsomal preparations, permeabilized cells, and lipid vesicles containing purified IP3 receptor. The purpose of the current study was to compare the effects of adenophostin-A and IP3 on Ca2+ release fro...

Intracellular Ca2+ is released from intracellular stores in the endoplasmic reticulum (ER) in response to the second messenger inositol (1,4,5) trisphosphate (InsP3) [1,2]. Then, a poorly understood cellular mechanism, termed capacitative Ca2+ entry, is activated [3,4]; this permits Ca2+ to enter cells through Ca(2+)-selective Ca(2+)-release-activated ion channels [5,6] as well as through less ...

This study used imaging and electrophysiological techniques in salamander retinal slices to correlate Ca2+ and Cl- levels in rods and thus test the hypothesis of a feedback interaction between Ca2+- and Ca2+-activated Cl- channels whereby Cl- efflux through Cl- channels can inhibit Ca2+ channels. Increasing [K+]o levels produced a concentration-dependent depolarization of rods accompanied by in...

Ion channels are responsible for control of cell function in excitable tissues such as heart and brain and also in organs and tissues traditionally thought to be non- excitable including liver and epithelium. In the present research, the effect of lead (Pb2+) on Ca2+ -dependent action potential and currents was studied in F77 neuronal soma membrane of Helix aspersa. For this purpose, action pot...

Neurotransmitter release is triggered by the cooperative action of approximately five Ca2+ ions entering the presynaptic terminal through Ca2+ channels. Depending on the organization of the active zone (AZ), influx through one or many channels may be needed to cause fusion of a vesicle. Using a combination of experiments and modeling, we examined the number of channels that contribute Ca2+ for ...

Spontaneous, localized intracellular Ca2+concentration ([Ca2+]i) transients (Ca2+ sparks) in skeletal, cardiac, and smooth muscle cells are thought to represent Ca2+ release through ryanodine-receptor (RyR) channels. In porcine tracheal smooth muscle (TSM) cells, ACh induces propagating [Ca2+]ioscillations that also represent Ca2+ release through RyR channels. We used real-time confocal imaging...

Low threshold Ca2+ currents mediated by T-type channels underlie burst spike activities of relay neurons in the thalamus. We have previously reported that knock-out mice for T-type channels show an enhanced nociceptive response to visceral pain, accompanied by an increase in tonic spikes in the absence of burst spikes in thalamic relay neurons. These results raised a possibility that T-type cha...

We studied the contribution of L-type Ca2+ channels to action potential-evoked Ca2+ influx in dendritic spines of CA1 pyramidal neurons and the modulation of these channels by the beta2 adrenergic receptor. Backpropagating action potentials (bAPs) (three at 50 Hz) were evoked by brief somatic current injections, and Ca2+ transients were recorded in proximal basal dendrites and associated spines...