A small-molecule TrkB ligand restores hippocampal synaptic plasticity and object location memory in Rett syndrome mice.

Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in methyl-CpG-binding protein-2 (), a transcriptional regulator of many genes, including brain-derived neurotrophic factor (). BDNF levels are reduced in RTT autopsy brains and in multiple brain areas of -deficient mice. Furthermore, experimental interventions that increase BDNF levels improve RTT-like phenotypes in mutant mice. Here, we characterized the actions of a small-molecule ligand of the BDNF receptor TrkB in hippocampal function in mutant mice. Systemic treatment of female heterozygous (HET) mice with LM22A-4 for 4 weeks improved hippocampal-dependent object location memory and restored hippocampal long-term potentiation (LTP). Mechanistically, LM22A-4 acts to dampen hyperactive hippocampal network activity, reduce the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs), and reduce the frequency of spontaneous tetrodotoxin-resistant Ca signals in mutant hippocampal neurons, making them comparable to those features observed in wild-type neurons. Together, these observations indicate that LM22A-4 is a promising therapeutic candidate for the treatment of hippocampal dysfunction in RTT.