Combined Light and Electron Microscopic Visualization of Neuropeptides and Their Receptors in Central Neurons
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The study of neuronal connections and neuron to neuron (or neuron to glia) communication is of fundamental importance in understanding
brain structure and function. Therefore, ultrastructural investigation by the use of immunocytochemical techniques is a really
precious tool to obtain an exact map of the localization of neurotransmitters (neuropeptides) and their receptors at different
types of synapses. However, in immunocytochemical procedures one has always to search for the optimal compromise between structural
preservation and retention of antigenicity. This is often made difficult by the need to localize not only small transmitter
molecules, as in the case of transmitter amino acids and neuropeptides, but also their specific receptors that are usually
large proteins very sensitive to fixation procedures.
We describe here a preembedding procedure employing the Fluoronanogold™ reagent, a probe consisting of fluorescein-tagged
antibodies conjugated with ultrasmall gold particles that can be made visible under the electron microscope by a gold intensification
procedure. This technique permits correlative fluorescence and electron microscopy observations, providing a very useful tool
for the study of neuronal connectivity. Moreover, the Fluoronanogold™ procedure can be combined with conventional postembedding
immunogold techniques in multiple labeling studies.
