Brain-derived neurotrophic factor Val66Met allele impairs basal and ketamine-stimulated synaptogenesis in prefrontal cortex.
BACKGROUND
Knock-in mice with the common human brain-derived neurotrophic factor (BDNF) Val66Met polymorphism have impaired trafficking of BDNF messenger RNA to dendrites. It was hypothesized, given evidence that local synapse formation is dependent on dendritic translation of BDNF messenger RNA, that loss-of-function Met allele mice would show synaptic deficits both at baseline and in response to ketamine, an N-methyl-D-aspartate antagonist that stimulates synaptogenesis in prefrontal cortex (PFC).


METHODS
Whole-cell recordings from layer V medial PFC pyramidal cells in brain slices were combined with two-photon laser scanning for analysis of wildtype, Val/Met, and Met/Met mice both at baseline and in response to a low dose of ketamine.


RESULTS
Val/Met and Met/Met mice were found to have constitutive atrophy of distal apical dendrites and decrements in apically targeted excitatory postsynaptic currents in layer V pyramidal cells of PFC. In addition, spine density and diameter were decreased, indicative of impaired synaptic formation/maturation (synaptogenesis). In Met/Met mice the synaptogenic effect of ketamine was markedly impaired, consistent with the idea that synaptogenesis is dependent on dendritic translation/release of BDNF. In parallel behavioral studies, we found that the antidepressant response to ketamine in the forced swim test was blocked in Met/Met mice.


CONCLUSIONS
The results demonstrate that expression of the BDNF Met allele in mice results in basal synaptic deficits and blocks synaptogenic and antidepressant actions of ketamine in PFC, suggesting that the therapeutic response to this drug might be attenuated or blocked in depressed patients who carry the loss of function Met allele.
Department of Psychiatry, Yale School of Medicine, New Haven, Connecticut, USA.
Rong-Jian
RJ
Liu
Francis S
FS
Lee
Xiao-Yuan
XY
Li
Francis
F
Bambico
Ronald S
RS
Duman
George K
GK
Aghajanian
D000483:Alleles; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics* / Q000378:metabolism*; D003712:Dendrites / Q000378:metabolism; D003865:Major Depressive Disorder / Q000235:genetics / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D007649:Ketamine / Q000494:pharmacology; D051379:Mice; D008822:Mice, Transgenic; D018408:Patch-Clamp Techniques; D011110:Polymorphism, Genetic; D017397:Prefrontal Cortex / Q000378:metabolism*; D017966:Pyramidal Cells / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D013569:Synapses / Q000378:metabolism*
D019208:Brain-Derived Neurotrophic Factor; D018691:Excitatory Amino Acid Antagonists; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D007649:Ketamine