Physiology of Bergmann glial cells.

While Bergmann glial cells play an important role in the development of the cerebellum they were thought to serve as passive insulators of the Purkinje cell dendritic tree and its synaptic connections. New results challenge this view and demonstrate that Bergmann glial cells are equipped with a large repertoire of receptors allowing them to sense the activity of synapses. These receptors have distinct biophysical and pharmacological features activating second-messenger pathways in the Bergmann glial cells. It is evident that the synapse has to be viewed as consisting of three elements, the presynaptic and postsynaptic region and the glial ensheathment. All three elements of this synaptic complex may undergo plastic changes as a prerequisite for central nervous system plasticity. Glial cells could interfere with synaptic transmission by communicating with neurons via the extracellular space, e.g., by modulating ion concentrations or transmitter levels in the cleft (Fig. 6).