We examined the effects of recent discharge activity on [Ca2+]i in neocortical pyramidal cells. Our data confirm and extend the observation that there is a linear relationship between plateau [Ca2+]i and firing frequency in soma and proximal apical dendrites. The rise in [Ca2+] activates K+ channels underlying the afterhyperpolarization (AHP), which consists of 2 Ca(2+)-dependent components: th...

Single pituitary gonadotrophs exhibit episodes of spontaneous fluctuations in cytoplasmic calcium concentration [( Ca2+]i) due to entry through voltage-sensitive calcium channels (VSCC) and show prominent agonist-induced oscillations in [Ca2+]i that are generated by periodic release of intracellular Ca2+. Gonadotropin releasing hormone (GnRH) elicited three types of Ca2+ responses: at low doses...

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...

Light accelerates degeneration of photoreceptor cells of the retinal degeneration B (rdgB) mutant of Drosophila. During early stages of degeneration, light stimuli evoke spikes from photoreceptors of the mutant fly; no spikes can be recorded from photoreceptors of the wild-type fly. Production of spike potentials from mutant photoreceptors was blocked by diltiazem, verapamil hydrochloride, and ...

Phospholipase C (PLC) regulates various cellular processes by catalyzing the formation of inositol-1,4,5-trisphosphate (IP3) and diacylglycerol from phosphatidylinositol-4,5-bisphosphate (PIP2). Here, we have investigated the influence of Ca2+ on receptor-triggered PLC activity in individual insulin-secreting beta-cells. Evanescent wave microscopy was used to record PLC activity using green flu...

Fast-twitch skeletal muscle fibers are often exposed to motor neuron double discharges (≥200 Hz), which markedly increase both the rate of contraction and the magnitude of the resulting force responses. However, the mechanism responsible for these effects is poorly understood, likely because of technical limitations in previous studies. In this study, we measured cytosolic Ca2+ during doublet a...

The transduction of many cellular stimuli results in oscillations in the intracellular concentration of calcium ions (Ca2+). Although information is thought to be encoded in the frequency of such oscillations, no frequency decoder has been identified. Rapid superfusion of immobilized Ca2+- and calmodulin-dependent protein kinase II (CaM kinase II) in vitro showed that the enzyme can decode the ...

HCN1 hyperpolarization-activated cation channels act as an inhibitory constraint of both spatial learning and synaptic integration and long-term plasticity in the distal dendrites of hippocampal CA1 pyramidal neurons. However, as HCN1 channels provide an excitatory current, the mechanism of their inhibitory action remains unclear. Here we report that HCN1 channels also constrain CA1 distal dend...

Complexity of Intracellular Caz+ Signals Ca2+ is a ubiquitous intracellular signaling molecule controlling a wide array of cellular processes, including secretion, contraction, and cell proliferation (Berridge, 1993; Clapham, 1995). In resting cells, the intracellular Ca2+ concentration ([Cap+],) is maintained at approximately 1 O-l 00 nM, and during stimulation the average [Ca2+li can rise up ...

The mechanism of transmitter release by intracellular Ca has been explored by recording presynaptic Ca concentration ([Ca2+]i) with Ca-sensitive fluorescent dyes and by controlling [Ca2+]i with photosensitive Ca chelators. [Ca2+]i decays slowly (in seconds) after presynaptic action potentials, while transmitter release lasts only a few ms after each spike at fast synapses. Simulations of Ca dif...