Tomas Bellamy
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Neuron to astrocyte signalling in the cerebellum

The brain is composed of a complex network of around 100 billion neurons which are connected to one another by synapses; tiny junctions at which electrical impulses trigger the release of chemical neurotransmitters into the synaptic cleft to stimulate the adjacent cell. This network of electrical and chemical signalling pathways is the means by which the brain carries out its main function - information processing. Neurons, however, are outnumbered in the brain more than ten to one by another class of cells known as glia.

Glia are electrically passive, and have long been known as supporting cells which supply metabolic intermediates to neurons, as well as maintaining a microenvironment favourable to electrical and synaptic signalling through uptake of neurotransmitters and buffering of external K+ ion concentration. More recently, a class of glia, known as astrocytes, has come to prominence with the discovery that these cells express neurotransmitter receptors which are activated during synaptic transmission. While incapable of propagating action potentials, astrocytes can instead communicate through a number of second messenger signalling pathways that are engaged by receptor activation. Thus, astrocytes respond to synaptic activity by initiating biochemical signalling pathways, principally through the elevation of intracellular Ca2+.

The major interest of our group is in understanding the role of bi-directional communication between neurons and glia in brain physiology. Specifically, we are interested in how information contained in neuronal network activity is encoded by astrocytes into Ca2+ signals, with particular emphasis on the importance of kinetics in signal transduction. To that end, we use the cerebellum - a region of the brain involved in motor coordination and learning - to study the spatiotemporal properties of the glutamate and nitric oxide signalling pathways in astrocytes. We are also interested in the consequences of astrocyte Ca2+ signalling on neuronal network function, focussing on how astrocytes can modulate synaptic strength.