A Simple and Rapid Immunocytochemical Assay for Quantifying Surface Receptor Abundance in Cultured Cells

Synaptic transmission is a fundamental process through which neurons communicate. This mechanism involves the release of neurotransmitters-such as GABA, glutamate, and norepinephrine-via exocytosis from presynaptic axon terminals. These neurotransmitters are recognized by specific receptors, including GABAR, AMPAR, and β₂AR, located on the dendritic spine membranes of postsynaptic neurons. The receptors are highly dynamic on the plasma membrane. Conventional immunocytochemical techniques label only the total expression of receptors (Simultaneously labeling all receptors on the membrane surface and within the cells) in cultured cells. Although this provides valuable information for assessing receptor abundance, it does not allow for a precise comparison of whether the number of receptors located on the cell membrane surface has changed. Here, we introduce a method for labeling plasma membrane receptors in neuronal cells using surface immunocytochemistry. By selecting antibodies that specifically recognize the extracellular domain of the receptor, receptors on the cell membrane surface can be labeled outside the intact, impermeable cell membrane.