Co-labeling of Neuronal Cells Using DiI Neuronal Filling and Immunohistochemistry to Explore Metabotropic Glutamate Receptor Expression

Neuronal morphology, including microarchitecture, can provide insightful information regarding neuronal physiology. Dendritic spines are highly plastic and responsive to neurotransmitter binding, such as glutamate. It is clear that structural plasticity is related to changes in synaptic efficacy, which is heavily mediated by receptor expression. Using a combination of diolistic labeling of neurons using lipophilic fluorescent dye and immunohistochemistry, neuronal morphology and receptor expression can provide beneficial information regarding neuronal modifications and physiology following external stimuli. Here we describe a method for co-labeling of neuronal morphology, using diolistic labeling, and metabotropic glutamate receptor expression, using immunohistochemistry. The overarching goal of this chapter is to discuss the background of these techniques, review beneficial output measurements and inferences that can be made from quantitative data collected using this technique, and provide a standardized protocol for achieving optimal results. While variations in this protocol can be used, this chapter contains general information that will facilitate the researcher’s ability to conduct co-labeling experiments, especially those exploring research questions related to metabotropic glutamate receptor expression within the mammalian brain.