Brain-derived neurotrophic factor (BDNF) exerts its trophic and neuromodulatory effects by acting on the high-affinity specific receptor trkB. To obtain precise information on the subcellular localization of BDNF and trkB receptors in neurons and their synapses we here present two immunohistochemical techniques used for ultrastructural investigations: a post-embedding immunogold staining protocol for detecting BDNF and a pre-embedding FluoronanogoldTM immunostaining method to detect trkB receptors, by using secondary fluorescein-tagged antibodies conjugated with ultrasmall gold particles. Moreover, we describe here how to combine the two procedures in the same tissue samples for BDNF/trkB multiple labelling studies.