Intracellular Communication Using Calcium Waves in Dendritic Spines

Intracellular communication involves understanding the conditions under which excitable calcium waves can propagate in the tortuous domains created by the spines and dendrites of neurons (see Figure 1).

Fluorescent imaging of a whole neuron showing the soma and dendritic arbor

This research requires close collaboration between an experimental team (lead by Professor. A. Fine at the MRC, Mill Hill) involved in the development of new high resolution optical methods for studying calcium propagation in real-time in neurons (see Figure 2), combined with the development of advanced algorithms for simulating excitable calcium dynamics in neurons. These simulations need to include the effect of presynaptic electrical stimulation on calcium fluxes through the ionic in the postsynaptic membrane of the dendritic spines, CICR from internal stores at the base of the spines and the role of morphology in internal neuronal communication.

Confocal Imaging of Calcium Transients within Individual Dendritic Spines Evoked by Afferent Stimulation.(i) The postsynaptic spine stimulated lies at the targeted point;(ii) A calcium transient is evoked after two presynaptic stimuli have been applied, time is plotted along the x-axis while the y-axis is the one-dimensional spatial cut shown in (i);(iii) A postsynaptic calcium transient is evoked after a single small stimulus is applied. The lower images show postsynaptic calcium fluorescence changes induced by the stimulation in response to the presynaptic electrical stimulation (mV).

We are investigating several aspects of the encoding, transmission and decoding of calcium signals in neurons including: the influence of presynaptic stimulation and morphology on calcium encoding in spines; the relation between the distribution of internal stores and signal transmission and decoding between neighbouring spines on a dendritic shaft; what happens to calcium waves at branch points of the dendritic arbor; and what are the conditions under which excitable calcium waves can propagate in the whole dendritic arbor and reach the soma? This research will involve detailed parallel simulations based on biologically constrained criteria for calcium diffusion, buffering, pumping and excitable release from internal stores.

Related Publications

Stephan Pencea and H.G.E. Hentschel, Spatiotemporal Chaos in Calcium Oscillations. (In preparation, 2000).