Use of two anterograde axon tracers to label distinct cortical neuronal populations located in close proximity.
In order to investigate converging projections originating from adjacent populations of cortical neurons, injections of two different anterograde tracers, biotinylated dextranamine (BDA) and Phaseolus vulgaris leucoagglutinin (PHA-L), were made in close proximity. When the two injection sites were separated by around 500 microm and the time between injections was 1--4 h, BDA-labeling of neuronal elements was found not only at the BDA injection site but also at the PHA-L injection site. This false-positive BDA labeling of neurons at the PHA-L injection site was so intense that labeled axons could be traced, both into the neighboring cortical gray matter and into white matter. Increasing the separation distance to 1000 microm resulted in much fewer falsely positive labeled neurons at the PHA-L injection site. Even more effective was extending the time interval between the two injections. Thus, if the BDA injection preceded the PHA-L injection by more than 12 h, virtually no false-positive labeling was associated with the PHA-L injection site. These procedures may be applied to other combinations of anterograde tracers, such as BDA with tetramethylrhodamine-conjugated dextran amine.
Ojima
H
H
Cortical Organization and Systematics, BSI, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. yojima@brain.riken.go.jp
Takayanagi
M
M
D000818:Animals; D001303:Auditory Cortex / Q000378:metabolism* / Q000502:physiology; D001370:Axonal Transport / Q000502:physiology*; D001369:Axons / Q000378:metabolism / Q000502:physiology*; D001710:Biotin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism; D002415:Cats; D003911:Dextrans / Q000008:administration & dosage / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D010835:Phytohemagglutinins / Q000008:administration & dosage / Q000378:metabolism
D003911:Dextrans; D005456:Fluorescent Dyes; D010835:Phytohemagglutinins; C076397:biotinylated dextran amine; C100156:leukoagglutinins, plants; D001710:Biotin