Alterations in BDNF and synapsin I within the occipital cortex and hippocampus after mild traumatic brain injury in the developing rat: reflections of injury-induced neuroplasticity.
Brain-derived neurotrophic factor (BDNF), its signal transduction receptor trkB, and its downstream effector, synapsin I, were measured in the hippocampus and occipital cortex of young animals after fluid-percussion brain injury (FPI). Isofluorane anaesthetized postnatal day 19 rats were subjected to a mild lateral FPI or sham injury. Rats were sacrificed at 24 h, 7 days, or 14 days after injury in order to determine mRNA expression. Additional animals were sacrificed at 7 and 14 days after injury for protein analysis. Only FPI animals exhibited hemispheric differences in BDNF levels. These animals exhibited a contralateral increase, ranging from 40% to 75%, in BDNF mRNA within both the hippocampus and occipital cortex at 24 h and 7 days after injury. The increase in message within the occipital cortex was accompanied by an increase in BDNF protein at 7 and 14 days after injury. However, hippocampal BDNF protein increased in both hemispheres at postinjury day 7 and was restricted to the ipsilateral hippocampus at postinjury day 14. At postinjury day 7, both trkB and synapsin I mRNA expression increased ipsilaterally and decreased contralaterally in the occipital cortex. In addition, synapsin I phosphorylation was increased by 20% in the ipsilateral cortex and by 30% in the hippocampus on this day. These results indicate that the developing brain responds to a mild injury by modifying factors related to synaptic plasticity and suggest that regions remote from the site of injury express neurotrophic signals potentially needed for compensatory responses.
Division of Neurosurgery, Department of Surgery, UCLA School of Medicine, Los Angeles, California 90024-7039, USA. ggriesbach@mednet.ucla.edu
Grace Sophia
GS
Griesbach
David Allen
DA
Hovda
Raffaella
R
Molteni
Fernando
F
Gomez-Pinilla
D000818:Animals; D000831:Animals, Newborn; D001930:Brain Injuries / Q000378:metabolism*; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006624:Hippocampus / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D009473:Neuronal Plasticity / Q000235:genetics; D009778:Occipital Lobe / Q000254:growth & development / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020813:Receptor, trkB / Q000096:biosynthesis / Q000235:genetics; D016704:Synapsins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D019208:Brain-Derived Neurotrophic Factor; D010750:Phosphoproteins; D012333:RNA, Messenger; D016704:Synapsins; D020813:Receptor, trkB