Fluorogold labeling of descending brain neurons in larval lamprey does not cause cell death.
In our previous double-labeling studies, the fluorescent anatomical tracers Fluorogold (FG) and Texas red dextran amine (TRDA) were used to demonstrate that descending brain neurons, approximately 80% of which are reticulospinal (RS) neurons, in spinal cord-transected larval lamprey regenerate their axons. However, the numbers of FG-labeled descending brain neurons decreased significantly with increasing recovery times, from 2 to 16 weeks. For some FG-labeled mammalian neurons, FG appears to degrade and/or be lost over time, while in other neurons this tracer can kill neurons. In the present study, these possibilities were examined in larval lamprey for FG-labeled descending brain neurons. As in our previous studies, FG was applied to the spinal cord at 40% body length (BL, relative distance from the head) to retrogradely labeled descending brain neurons, and after recovery times of 2, 8, or 16 weeks, HRP, a non-toxic retrograde tracer, was applied to the spinal cord at 20% BL to determine if the numbers of HRP-labeled neurons were reduced. At these three recovery times, the numbers of HRP-labeled descending brain neurons were not significantly different than the numbers of HRP-labeled neurons in control animals that were not labeled with FG. Furthermore, the size and morphology of cell bodies and dendritic trees were not noticeably different in descending brain neurons with and without FG. Thus, in larval lamprey, FG does not appear to kill these neurons, but some FG probably is degraded and/or lost from neurons with increasing recovery times.
Division of Biological Sciences and Interdisciplinary Neuroscience Program, 114 Lefevre Hall, University of Missouri, Columbia, MO 65211-6190, USA.
Andrew D
AD
McClellan
Lei
L
Zhang
Ryan
R
Palmer
D000818:Animals; D001933:Brain Stem / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002452:Cell Count; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D004525:Efferent Pathways / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism / Q000633:toxicity; D020439:Growth Cones / Q000187:drug effects / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism / Q000633:toxicity; D007798:Lampreys / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism*; D007814:Larva / Q000033:anatomy & histology / Q000378:metabolism*; D009410:Nerve Degeneration / Q000139:chemically induced* / Q000503:physiopathology; D009416:Nerve Regeneration / Q000502:physiology; D009498:Neurotoxins / Q000378:metabolism / Q000633:toxicity; D012154:Reticular Formation / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013119:Spinal Cord Injuries / Q000503:physiopathology; D013194:Staining and Labeling / Q000379:methods; D013266:Stilbamidines / Q000378:metabolism / Q000633:toxicity*; D013997:Time Factors
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D009498:Neurotoxins; D013266:Stilbamidines; D006735:Horseradish Peroxidase