Endogenous brain-derived neurotrophic factor protects dopaminergic nigral neurons against transneuronal degeneration induced by striatal excitotoxic injury.
Injury to the central nervous system causes atrophy or death of connecting neurons and can modify the expression of neurotrophic factors. We observed transneuronal upregulation of brain-derived neurotrophic factor (BDNF) expression in the rat ipsilateral substantia nigra pars compacta after a striatal lesion induced by kainate. This effect is developmentally regulated because the enhancement of nigral BDNF expression was only observed when striatal lesion was performed on postnatal day (P) 15 and in adulthood, but not at P7. Interestingly, the lack of regulation of BDNF was coincident with the transynaptic degeneration of nigral neurons after striatal excitotoxic injury. Hence, the number of tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta decreased when the lesion was performed at P7, but not at P15 or at P30. The analysis of the functional significance of this BDNF upregulation was done using trkB-IgG fusion proteins. After striatal injury, blockade of endogenous BDNF by trkB fusion proteins induced an atrophy of the dopaminergic neurons of the pars compacta. The injection of trkB-IgG fusion proteins did not modify the effects of kainate in the substantia nigra pars reticulata. Thus, our results show that BDNF exerts an autocrine/paracrine protective effect selectively on dopaminergic neurons against the loss of trophic support from the target striatum.
Canudas
Anna M
AM
Departament de Biologia Cel lular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona, IDIBAPS, Casanova 143, E-08036 Barcelona, Spain.
Pezzi
Susana
S
Canals
Josep M
JM
Pallàs
Mercè
M
Alberch
Jordi
J
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern / Q000379:methods; D001930:Brain Injuries / Q000139:chemically induced / Q000150:complications / Q000517:prevention & control; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism*; D002452:Cell Count; D003342:Corpus Striatum / Q000187:drug effects / Q000503:physiopathology*; D003952:Diagnostic Imaging / Q000379:methods; D004298:Dopamine / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D007839:Functional Laterality / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D007074:Immunoglobulin G / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D007608:Kainic Acid; D008297:Male; D009410:Nerve Degeneration / Q000209:etiology / Q000517:prevention & control*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020813:Receptor, trkB / Q000276:immunology; D013378:Substantia Nigra / Q000166:cytology*; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
D019208:Brain-Derived Neurotrophic Factor; D007074:Immunoglobulin G; D014446:Tyrosine 3-Monooxygenase; D020813:Receptor, trkB; D007608:Kainic Acid; D004298:Dopamine