BDNF-induced facilitation of afferent-evoked responses in lamina II neurons is reduced after neonatal spinal cord contusion injury.
We previously reported that brain-derived neurotrophic factor (BDNF), a pronociceptive neurotransmitter, induces synaptic facilitation of excitatory postsynaptic current (EPSC) in lamina II neurons of neonatal rats up to P14 in a N-methyl-d-aspartate (NMDA) receptor-dependent manner. Here we used the patch-clamp technique to study synaptic and NMDA-evoked responses in transverse spinal slices in the lumbar enlargement as well as the ability of BDNF to modify these responses from 1 day to 6 wk after neonatal contusion. In older uninjured animals (>P14), BDNF continued to evoke synaptic facilitation although superfusion of NMDA (in TTX) induced inward current of significantly smaller amplitude than that observed in younger rats. After contusion injury, BDNF was unable to facilitate dorsal root-evoked EPSCs in lamina II neurons despite the finding that NMDA-evoked currents were only slightly smaller than those observed in age-matched uninjured animals. These findings suggest that although BDNF-induced facilitation of the AMPA/kainate receptor-mediated response to dorsal root stimulation is maintained in the mature dorsal horn from intact rats, BDNF may no longer elicit these pronociceptive actions after neonatal contusion injury. The lack of change in NMDA-evoked currents in contused cords suggests that diminished NMDA receptor function is not the major cause of the decline in BDNF action after contusion. It seems more likely that diminished trkB expression and enhanced expression of truncated trkB receptors in the contused cord play a significant role in determining the reduced effect of BDNF under these conditions.
Garraway
Sandra M
SM
Department of Neurobiology and Behavior, 550 Life Sciences Bldg., State University of New York, Stony Brook, New York 11794-5230, USA.
Anderson
Aileen J
AJ
Mendell
Lorne M
LM
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000344:Afferent Pathways / Q000187:drug effects / Q000503:physiopathology / Q000528:radiation effects; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D066298:In Vitro Techniques; D034921:Lamin Type B / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000473:pathology*; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D019208:Brain-Derived Neurotrophic Factor; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D034921:Lamin Type B; D016202:N-Methylaspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; C056639:2-amino-5-phosphopentanoic acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D014633:Valine