Purinergic junctional transmission and propagation of calcium waves in spinal cord astrocyte networks |
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| Authors: | Bennett Max R Buljan Vlado Farnell Les Gibson William G |
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| Affiliation: | The Neurobiology Laboratory, Department of Physiology, Institute for Biomedical Research, The School of Mathematics and Statistics, The University of Sydney, New South Wales, Australia. maxb@physiol.usyd.edu.au |
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| Abstract: | Micro-photolithographic methods have been employed to form discrete patterns of spinal cord astrocytes that allow quantitative measurements of Ca(2+) wave propagation. Astrocytes were confined to lanes 20-100 microm wide and Ca(2+) waves propagated from a point of mechanical stimulation or of application of adenosine triphosphate; all Ca(2+) wave propagation was blocked by simultaneous application of purinergic P2Y(1) and P2Y(2) antagonists. Stimulation of an astrocyte at one end of a lane, followed by further stimulation of this astrocyte, gave rise to Ca(2+) transients in the same astrocytes; however, if the second stimulation was applied to an astrocyte at the other end of the lane, then this gave rise to a different but overlapping set of astrocytes generating a Ca(2+) signal. Both the amplitude and velocity of the Ca(2+) wave decreased over 270 microm from the point of initiation, and thereafter remained, on average, constant with random variations for at least a further 350 microm. Also, the percentage of astrocytes that gave a Ca(2+) transient decreased with distance along lanes. All the above observations were quantitatively predicted by our recent theoretical model of purinergic junctional transmission, as was the Ca(2+) wave propagation along and between parallel lanes of astrocytes different distances apart. These observations show that a model in which the main determinants are the diffusion of adenosine triphosphates regeneratively released from a stimulated astrocyte, together with differences in the properties and density of the purinergic P2Y receptors on astrocytes, is adequate to predict a wide range of Ca(2+) wave transmission and propagation phenomena. |
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