Ca2+ spikes

Short (typically lasting no more than a few seconds) increases in cytosolic Ca2+ concentration that periodically interrupts the stable resting level. Many Ca2+ signals are delivered to cells as frequency-coded Ca2+ spikes. 

FIG. 1. Phenylephrine (PE)-mediated asynchronous wave-like [Ca2+] oscillations and contraction in the rabbit inferior vena cava. (A) [Ca2+] oscillations recorded in neighbouring smooth muscle cells within the intact vessel are not synchronized between cells as they each display different frequency of oscillations. (B) Individual Ca2+ spike in PE-mediated [Ca2+]j oscillations are wave-like as different regions (1, 2 and 3) in the same ribbon-shaped VSMC experience sequential rise of [Ca2+] in time. (C) The [PE]-dependence in force generation is compared to the [PE]-dependence in the percentage recruitment of cells, the amplitude of the [Ca2+]j oscillations, the frequency of the [Ca2+]j oscillations and the apparent velocity of the recurring Ca2+ waves. (Experimental traces reproduced, with permission from Lee et al 2001.)... 

Burdjga Where localized high Ca2+ spiking occurs, we never see this translated into the mechanical response. These spikes can be as high as 10 //M locally. We have to consider that without a wave we are unable to switch on the contractile machinery. 

P6rez-Garci E, Gassmann M, BettlerB, Larkum ME (2006) The GABABib isoform mediates long-lasting inhibition of dendritic Ca2+ spikes in layer 5 somatosensory pyramidal neurons. Neuron 50 603-16... 

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