Secretion of catecholamines from individual bovine adrenal medullary cells grown in primary culture has been investigated with a carbon-fiber microelectrode placed adjacent to the cells. Oxidation of catecholamines at the electrode surface results in changes in current, which give a real-time measure of catecholamine secretion. Chemical agents are introduced to the individual cells by pressure ...

The temporal resolution of carbon-fiber microelectrodes has been exploited to examine the plasticity of quantal secretory events at individual adrenal medullary cells. The size of individual quantal events, monitored by amperometric oxidation of released catecholamines, was found to be dependent on the extracellular ionic composition, the secretagogue, and the order of depolarization delivery. ...

Synaptic interactions between the dendrites of mitral/tufted (MT) and granule cells (GCs) in the olfactory bulb are important for the determination of spatiotemporal firing patterns of MTs, which form an odor representation passed to higher brain centers. These synapses are subject to modulation from several sources originating both within and outside the bulb. We show that dopamine, presumably...

Synchronous neuronal firing can be induced in hippocampal slices in the absence of synaptic transmission by lowering extracellular Ca2+ and raising extracellular K+. However, the ionic mechanisms underlying this nonsynaptic synchronous firing are not well understood. In this study we have investigated the role of KCNQ/Kv7 channels in regulating this form of nonsynaptic bursting activity. Incuba...

Ca(2+)-mobilizing hormones induce oscillations in the cytoplasmic concentration of free Ca2+ ('free Ca') (spikes) in many cells. In hepatocytes the frequency of spiking depends on agonist dose, but the time course of an individual spike does not change with agonist concentration. Interestingly, the time course of individual spikes does depend on the hormone species, but the cellular mechanisms ...

Janssen, Luke J. Ionic mechanisms and Ca2 regulation in airway smooth muscle contraction: do the data contradict dogma? Am J Physiol Lung Cell Mol Physiol 282: L1161–L1178, 2002; 10.1152/ajplung.00452. 2001.—In general, excitation-contraction coupling in muscle is dependent on membrane depolarization and hyperpolarization to regulate the opening of voltage-dependent Ca2 channels and, thereby, i...

Neuronal firing patterns and frequencies determine the nature of encoded information of the neurons. Here we discuss the molecular identity and cellular mechanisms of spike-frequency adaptation in central nervous system (CNS) neurons. Calcium-activated potassium (KCa) channels such as BKCa and SKCa channels have long been known to be important mediators of spike adaptation via generation of a l...

The NMDA spike is a long-lasting nonlinear phenomenon initiated locally in the dendritic branches of a variety of cortical neurons. It plays a key role in synaptic plasticity and in single-neuron computations. Combining dynamic system theory and computational approaches, we now explore how the timing of synaptic inhibition affects the NMDA spike and its associated membrane current. When impingi...

The key trigger for Hebbian synaptic plasticity is influx of Ca2+ into postsynaptic dendritic spines. The magnitude of [Ca2+] increase caused by NMDA-receptor (NMDAR) and voltage-gated Ca2+ -channel (VGCC) activation is thought to determine both the amplitude and direction of synaptic plasticity by differential activation of Ca2+ -sensitive enzymes such as calmodulin. Ca2+ influx is negatively ...

The six-layered mammalian neocortex evolved from the three-layered paleocortex, which is retained in present-day reptiles such as the turtle. Thus the turtle offers an opportunity to examine which cellular and circuit properties are fundamental to cortical function. We characterized the dendritic properties of pyramidal neurons in different cortical regions of mature turtles, Pseudemys scripta ...