30 October 2009

Astrocytes: The Power Behind the Neuronal Throne?

Scientists are learning more about an interesting brain cell known as an astrocyte. Astrocytes are glial cells, or support cells of the brain. But is it possible that astrocytes were never told that they are mere support cells?
Scientists at Yale, most notably Ann H. Cornell-Bell and Steven Finkbeiner, have shown that calcium waves can spread from the point of stimulation of one astrocyte to all other astrocytes in an area hundreds of times the size of the original astrocyte. Furthermore, calcium waves can also cause neurons to fire. And calcium waves in the cortex are leading scientists to infer that this style of communication may be conducive to the processing of certain thoughts. If that isn't convincing, it was recently shown that a molecule that stimulates the same receptors as THC can ignite astrocyte calcium release. _SciAm
Those are the words of neuroscientist Andrew Koob, author of the book "The Root of Thought," which suggests that astrocytes may be an important key to human consciousness. Glia are the most numerous cells in the brain, and are crucial to the survival of neurons. But until recently, no one believed that astroglia may be active participants in human consciousness itself.

The means by which astrocytes may alter and control human consciousness is thought to be "the calcium wave."
Interestingly, astrocytes are excitable cells like neurons. They base their communication on spontaneous or evoked cytosolic Ca2+ variations, instead of membrane electrical transients. Their remarkable morphology supports intercellular signaling as they form interconnected networks of cells coupled by gap-junctions, where each unit occupies a virtually non-overlapping domain of the inter-neuronal space. Surprisingly, astrocytes communicate also to neurons and synapses. In fact, they extend membrane processes to simultaneously contact hundreds of neuronal dendrites, thousands of synapses and even blood vessels. Indeed, astrocytes control the vasculature tone and they are likely to sense neuronal energy-demand and gate its consumption. Their physiology is thus bidirectionally linked to neuronal and synaptic activity, as they are capable of selectively respond to it on a millisecond time scale, by releasing specific neuroactive molecules (Ni et al., 2007). Notable are the discoveries of the -interaction with synaptic physiology and plasticity that led to -revisiting -information transfer between neurons, with the proposed concept of a “tri-partite synapse” (Perea and Araque, 2002). _frontiers
Actually, science has just begun to understand astrocytes. Beneath the level of the "calcium wave" is the "calcium oscillation". Calcium oscillations occur within individual astrocytes spontaneously within the hippocampus -- the seat of human long-term memory formation. Connections between calcium oscillations, calcium waves, neuronal oscillations, and various neuronal correlates of consciousness, will take time to locate and solidify. Stay tuned, and don't forget to drink your high calcium beverage of choice.

Labels: , ,

Bookmark and Share


Post a Comment

“During times of universal deceit, telling the truth becomes a revolutionary act” _George Orwell

<< Home

Newer Posts Older Posts