Figure 1.

Increased spontaneous excitatory neurotransmission and synapse formation in immature hippocampal neurons (5 DIV) following 18–24 h of treatment with the histone deacetylase inhibitor TSA. A, Schematic timeline of the experiment. B–D, Spontaneous excitatory synaptic currents upon 250 nm TSA treatments for 18–24 h. B, Representative recording of miniature excitatory events in DMSO and TSA-treated neurons recorded in 1 μm tetrodotoxin and 50 μm picrotoxin. C, Bar graph depicts the significant increase in mEPSC frequency following TSA treatment. The numbers in the bars denote the number of neurons recorded for each condition. D, Bar graph of mEPSC amplitude reveals no change following TSA treatment. E–G, Representative images of immunostaining of young hippocampal culture (5 DIV). Immunostaining was performed using synapsin (red) and PSD-95 (green) antibodies. White arrows indicate the colocalized puncta. H–J, Bar graphs depict the number of synapsin puncta (H), PSD-95 puncta (I), and colocalized synapsin and PSD-95 puncta (J) calculated from confocal images using ImageJ software. The immunocytochemistry was performed in triplicate in cultures from three independent experiments. K, Representative recordings of sucrose response. L, Bar graph depicting the charge/30 s calculated using mEPSC recordings upon application of 500 mm sucrose revealed a significant increase in sucrose response following TSA treatment (*p < 0.05 in this and all subsequent figures). M, Representative recordings depicting EPSCs evoked in response to action potential stimulation in cultures treated with either DMSO or 250 nm TSA. After TSA treatment an increased fraction of neurons exhibited response to stimulation compared with DMSO treatment. N, Cumulative histogram shows that a higher percentage of cells respond to evoked stimulation upon 250 nm TSA treatment compared with control DMSO treatment.