17 - Imaging Ion Channel Dynamics in Living Neurons by Fluorescence Microscopy

Abstract

This chapter discusses imaging ion channel dynamics in living neurons by fluorescence microscopy. The distribution of ion channels and receptors over the neuronal surface is important for the receipt of incoming synaptic inputs and for the integration of these inputs. Most voltage-gated and ligand-gated ion channels have nonhomogeneous distributions in the neuronal membrane; many are restricted to dendritic, axonal, or somatic domains and are further localized within these domains to regions such as dendritic spines, nodes of Ranvier, or synaptic junctions. Determining where and how ion channels are distributed and maintained is important for a variety of reasons. Ion channels in growth cones have a role in neurite outgrowth mechanisms; they are obligatory for synaptic transmission and are required for amplification of neurotransmitter signals in the postsynaptic membrane. Changes in ion-channel distributions are an important aspect in development and plasticity. Several neurological disorders, including multiple sclerosis, are characterized by a change in ion-channel distribution, which is partially responsible for the clinical manifestations of the disease. Fluorescence techniques are invaluable in the study of ion-channel and receptor distributions and dynamics. Fluorescence microscopy has extremely high sensitivity, the lower limit being the ability to detect a single fluorophore under optimal conditions. Fluorescence measurements are specified by the wavelengths of emission and excitation.