A typical neurocircuitry is consisted of different types of neurons and their synaptic connections that link both pre- and post-synaptic neurons into the circuit.Thus,selective elimination of a specific type of neurons,while keeping the rest of the neurons and circuitry intact,would be an important tool to investigate the functional roles of these neurons.Selective elimination of neurons from their circuitry can be produced by using various physical and chemical treatments,such as sectioning,suction,and electrical or chemical abolishment,as well as virus infection.However,these techniques suffer from a lack of specificity.Here,I describe an effective method that selectively eliminates a specific population of retinal ganglion cells (RGCs) (Ren et al,2013).First,the retrograde dye cholera toxin B subunit (CTB) was deposited at the superior colliculus (SC).Then,CTB was retrograde-transported to the retina,where it labeled retinal ganglion cells that innervate the SC.Next,CTB antibody was conjugated to Saporin (anti-CTB-SAP),forming an immunotoxin.This immunotoxin was injected intraocularly,allowing the CTB antibody to bind to the membrane of RGCs that were retrograde-labeled by CTB and enabling saporin to enter these cells and induce apoptosis.The entire process,from retrograde labeling to selective elimination of retrograde-labeled cells,takes about 14 days.Control experiments showed that RGCs that were not retrograde-labeled were intact after the treatment.Together,these results demonstrate an in vivo method that is effective in selectively abolishing a specific population of neurons.