Postsynaptic action of BDNF on GABAergic synaptic transmission in the superficial layers of the mouse superior colliculus.
The neurotrophin brain-derived neurotrophic factor (BDNF) is involved in numerous aspects of synapse development and plasticity. The present study was aimed at clarifying the significance of endogenous BDNF for the synaptically driven spontaneous network activity and GABAergic inhibition in the superficial layers of the mouse superior colliculus. In this structure neuron survival is unaffected by the absence of BDNF. Two experimental approaches were used: comparison of BDNF-deficient (-/-) and wild-type (+/+) mice and blockade of BDNF receptor signaling by the tyrosine kinase inhibitor K-252a. Patch-clamp recordings were performed on horizontal slices during postnatal days 15 and 16. The lack of BDNF in -/- mice caused a significant reduction of the spontaneous action potential frequency and an increase in the pharmacologically induced disinhibition of spike discharge. This change was accompanied by an increase in the amplitudes of GABAergic evoked, spontaneous, and miniature inhibitory postsynaptic currents (IPSCs). BDNF gene inactivation had no effect on the degree of paired-pulse facilitation or the frequency of miniature IPSCs. The increase of IPSC amplitudes by chronic BDNF deprivation was completely mimicked by acute exposure to K-252a in +/+ animals. The enhancement of GABAergic IPSCs in -/- animals was reversed by acute application of 100 ng/ml BDNF, but this rescue was completely prevented by blocking postsynaptic protein kinase C (PKC) activation with the PKC inhibitor peptide 19-31. From these results we conclude that BDNF increases spontaneous network activity by suppressing GABAergic inhibition, the site of action of BDNF is predominantly postsynaptic, BDNF-induced suppression of GABAergic synaptic transmission is caused by acute downregulation of GABA(A) receptors, and BDNF effects are mediated by its TrkB receptor and require PKC activation in the postsynaptic cell.
Henneberger
Christian
C
Developmental Physiology, Johannes Müller Institute of Physiology, Charité, D-10117 Berlin, Germany.
Jüttner
René
R
Rothe
Thomas
T
Grantyn
Rosemarie
R
D000200:Action Potentials; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013477:Superior Colliculi / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D019208:Brain-Derived Neurotrophic Factor; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D011493:Protein Kinase C; D001640:Bicuculline