BDNF sensitizes the response of lamina II neurons to high threshold primary afferent inputs.
Brain-derived neurotrophic factor (BDNF) is up-regulated and released in the dorsal horn following peripheral inflammation and has therefore been implicated in spinal mechanisms of sensitization. Despite these observations, the mechanisms associated with such a role for BDNF are not yet fully determined. Here, we investigate the effect of BDNF on dorsal root-evoked synaptic transmission in lamina II neurons. In a transverse spinal cord slice preparation from neonatal rats (P1-15), the whole cell patch-clamp technique was used to record from these neurons. Brief application of BDNF (50-200 ng/mL) facilitated the evoked synaptic currents; they remained enhanced even after BDNF was washed out. A significant minority of cells was minimally affected by BDNF and consistent with this, not all neurons in lamina II were immunoreactive for the tyrosine kinase (trk) B receptor. No facilitation was elicited when N-methyl-d-aspartate (NMDA) receptors were blocked with D-APV, when the postsynaptic NMDA receptors were selectively blocked with intracellular MK-801, or when postsynaptic neurons were loaded with BAPTA. Additionally, inhibiting phospholipase C (PLC) or protein kinase C (PKC) prior to BDNF application completely blocked facilitation. However, once synaptic current underwent BDNF-induced facilitation, the PKC inhibitors failed to reverse the effect, suggesting that PKC is needed for initiation, but not maintenance of BDNF-induced facilitation. These results demonstrate that BDNF functions at the spinal level to enhance synaptic efficacy in an NMDA receptor-dependent manner and requires the action of the PLC/PKC pathway. This action of BDNF may contribute to central sensitization and exaggerated pain states.
Garraway
Sandra M
SM
Department of Neurobiology and Behaviour, State University of New York, Stony Brook NY 11794-5230, USA.
Petruska
Jeffrey C
JC
Mendell
Lorne M
LM
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000502:physiology*; D007150:Immunohistochemistry; D009474:Neurons / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020813:Receptor, trkB / Q000032:analysis; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology* / Q000503:physiopathology; D009435:Synaptic Transmission / Q000187:drug effects*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology
D019208:Brain-Derived Neurotrophic Factor; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D004533:Egtazic Acid; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D020813:Receptor, trkB; D011493:Protein Kinase C; D010738:Type C Phospholipases; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid