Abstract: Neural nanoprobes are described, as well as methods for their use, including for use as a tagging system for neuronal pathway identification. The neural nanoprobes comprise metallic nanoparticles that are conjugated to both (i) a cationic polymer such as polyethylenimine and (ii) an antibody to a vesicular transporter protein. These methods allow retrograde characterization of glutamatergic neurons in a tissue slice preparation. Since the nanoparticles used are non-lipid-soluble and are specifically conjugated to enter and escape the synaptic vesicular machinery, these nanoparticles allow probing of a neuron's somatic origin, via the synapse, by diffusional means.