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J Eilers

Publications and source records attributed to J Eilers.

27 records · Page 2Linked to original sources
PubMed1995

Calcium signaling in a narrow somatic submembrane shell during synaptic activity in cerebellar Purkinje neurons.

Temporal and spatial changes in the intracellular Ca2+ concentration ([Ca2+]i) were examined in dendrites and somata of rat cerebellar Purkinje neurons by combining whole-cell patch-clamp recording and fast confocal laser-scanning microscopy. In cells loaded via the patch pipette with the high-affinity Ca2+ indicator Calcium Green-1 (Kd approximately 220 nM), a single synaptic climbing fiber response, a so-called complex spike, resulted in a transient elevation of [Ca2+]i that showed distinct differences among various subcellular compartments. With conventional imaging, the Ca2+ signals were prominent in the dendrites and almost absent in the soma. Confocal recordings from the somatic region, however, revealed steep transient increases in [Ca2+]i that were confined to a submembrane shell of 2- to 3-microns thickness. In the central parts of the soma [Ca2+]i increases were much slower and had smaller amplitudes. The kinetics and amplitudes of the changes in [Ca2+]i were analyzed in more detail by using the fast, low-affinity Ca2+ indicator Calcium Green-5N (Kd approximately 17 microM). We found that brief depolarizing pulses produced [Ca2+]i increases in a narrow somatic submembrane shell that resembled those seen in the dendrites. These results provide direct experimental evidence that the surface-to-volume ratio is a critical determinant of the spatiotemporal pattern of Ca2+ signals evoked by synaptic activity in neurons.

Animals↗
PubMed1995

Subthreshold synaptic Ca2+ signalling in fine dendrites and spines of cerebellar Purkinje neurons.

The conventional view of synaptic integration is that it results from the simple summation of electrical signals produced by each active synapse innervating a given neuron. However, because synaptic action can go beyond the production of postsynaptic electrical signals, to include intracellular biochemical events such as the generation of second messengers, it is possible that synaptic integration could occur at another level. We have considered this possibility by examining changes in the dendritic concentration of the second messenger, calcium, resulting from subthreshold excitatory synaptic activity in cerebellar Purkinje neurons. We report here clear evidence that such non-electrical synaptic integration occurs and that it takes place in restricted dendritic compartments consisting of spines and adjacent fine dendrites.

Action Potentials↗
PubMed1982

Reflex heating of the skin and telethermography.

Thermography is a very instructive method of showing the interaction between direct changes in heat radiation of the surface of the skin and its relation to reflex processes. Short reflex arcs, such as the axon reflex, and long reflex arcs, such as the flush phenomenon provoked by visceral cutaneous reflexes, can be illustrated by thermography. Reflex changes in skin temperature by cooling the skin of patients with cold contact urticaria with the short-term development of large areas of warmed skin and also reflex changes in cholinergic urticaria after prior heating of such skin areas where the urticarial eruption follows are reflected in the picture of telethermography. Reflex arcs between extremities affect the arterial blood flow and show individual variation, as in the case of the cessation of permanent local vasoconstriction by indirect cooling. The thermographic illustration of convective heat transport to the skin surface can be obstructed by the cooling effect of sweat secretion, e.g., water vapor exudation and by changes in conductive heat transport in abnormal skin.

Adult↗
PubMedDate not supplied

A new class of synaptic response involving calcium release in dendritic spines.

In the classical view, transmission of signals across synapses in the mammalian brain involves changes in the membrane potential of the postsynaptic cell. The use of high-resolution cellular imaging has revealed excitatory synapses at which postsynaptic, transient alterations in calcium ion concentration are tightly associated with electrical responses. Here, by investigating the synapse between parallel glutamatergic fibres and Purkinje cells in the mouse cerebellum, we identify a class of postsynaptic responses that consist of transient increases in dendritic Ca2+ concentration but not changes in somatic membrane potential. Our results indicate that these synaptic Ca2+ transients are mediated by activation of metabotropic glutamate-responsive mGluR1-type receptors and require inositol-1,4,5-trisphosphate-mediated Ca2+ release from intradendritic stores. The new type of synaptic response is restricted to postsynaptic microdomains, which range, depending on the frequency of stimulation, from individual spines to small spinodendritic compartments. Thus, the synaptic Ca2+-release signal may be one of the critical cues that determine the input specificity of long-term depression, a well-established form of activity-dependent plasticity at these synapses.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMedDate not supplied

Local dendritic Ca2+ signaling induces cerebellar long-term depression.

The coordinated activity of large numbers of adjacent parallel fiber synapses elevate calcium concentration locally in small regions of Purkinje cell dendrites. Such activity has also been reported to produce long-term depression of parallel fiber synaptic transmission. We have examined the relationship between these two events by combining patch clamp measurements of parallel fiber synaptic transmission with confocal microscopic imaging of the local calcium signals. We find that patterns of parallel fiber activity capable of evoking long-term depression invariably cause increases in Purkinje cell calcium concentration that are very spatially restricted. These results suggest that one function of the local dendritic calcium signals is to induce long-term depression of parallel fiber synapses.

Animals↗