Neurons in the brain have complicated electrical systems. In fact, a study by the University of Calgary Hotchkiss Brain Institute, Faculty of Medicine (Canada) has cleared up an important misconception about the way neurons generate signals. Ion channels are used by cells to manage the (minute) difference in electrical charge between the inside and the outside of the cell (the electrochemical gradient). All cells use these channels, but no organ more than the brain and no cells more than neurons. Neurons (brain cells) are known to use two types of channels: The A-type potassium channel, and the T-type calcium channel. It has always been thought that the two were separate and had independent tasks. This turns out not to be the case.
The investigators were following a hunch that the two channels might have some kind of relationship. Working in vitro (Petri dish) with rat cerebellum brain cells, they found that the A-type potassium channels, which control firing, dendritic activity, and synaptic integration, have in their channel complex calcium receptive proteins that can be activated by the T-type calcium channel. Through this link, the two channels form a signaling complex where the T-type calcium modulates the A-type channel. This is particularly important for feedback regulation of neuronal firing (one electrical system inhibits the output of another). This function is important in a wide range of electrically active cells (not just in the brain).
Principal Investigators, Ray W. Turner, Ph.D. and Gerald Zamponi, Ph.D. study the inhibitory and excitatory actions of ion channels in neurons of the cerebellum. Partnerships between the two laboratories, enabled Turner to ‘follow his hunch’ to prove that specific members of two different families of channels, previously thought to function independently, in fact function in tandem.
“The first results that revealed this link were amazing,” says Turner about this discovery. “These new developments redefine how we should look at the control of neuronal activity. They not only indicate how the timing of impulses from the cerebellum are controlled, but also predict how electrical activity in other parts of the brain is generated.”
While there are literally hundreds of studies based on brain scanning, showing that this or that section of the brain works with this or that brain function, there are far fewer fundamental studies such as this one. It reveals the workings of neuron cells at the molecular level, and the electrical activity at its most basic. While this is obviously a ‘small’ piece of the full story of how brain cells generate and coordinate electrical signals, it opens an important new avenue of approach – one that was not considered before.