Fig. 2: Acetylcholine release enhances excitatory–inhibitory balance for temporoammonic synaptic inputs relative to Schaffer collateral inputs.

A Middle, schematic representation of the experimental approach incorporating simultaneous recording of excitatory (V_h = −60 mV) and feedforward inhibitory (V_h = 0 mV) synaptic inputs from Schaffer collateral (SC) and temporoammonic (TA) input pathways to CA1 pyramidal neuron (bottom). Example traces for EPSCs and IPSCs in response to trains of 5 stimuli at 10 Hz to SC (green, left) and TA (purple, right) pathways before and after light stimulation (LED) of cholinergic fibres at 2 Hz for 5 min. B Change in paired-pulse ratio (PPR) after light stimulation of cholinergic fibres for excitatory and inhibitory responses to SC (left) and TA (right) pathway stimulation (5th stimuli PPR change for SC EPSC, n = 20 from 13 mice, p = 0.010; SC IPSC, p = 0.007; TA EPSC, p = 0.003; TA IPSC, p = 0.073). PPR is measured compared to the first response for each response in the train. C Comparison of synaptic Excitatory–Inhibitory (E–I) ratio before and after light stimulation measured by charge transfer at V_h = −60 mV and 0 mV for SC (left) and TA (right) input pathways (5th stimuli on SC E–I ratio, p = 0.059; TA E–I ratio, p = 0.007). D Comparison of synaptic E–I ratio between TA and SC input pathways before and after light stimulation. Acetylcholine release enhanced the overall relative synaptic charge transfer from the TA pathway (5th stimuli on TA-SC E–I ratio, p = 0.016). E–G similar quantification to B–D for experiments using bath applied exogenous carbachol (CCh, 10 µM) (E 5th stimuli PPR change for SC EPSC, n = 20 from 11 mice, p = 0.002; SC IPSC, p = 0.00002; TA EPSC, p = 0.0003; TA IPSC, p = 0.220. F 5th stimuli on SC E–I ratio, p = 0.285; TA E–I ratio, p = 0.0002. G 5th stimuli on TA-SC E–I ratio, p = 0.002). Data are mean ± SEM; comparisons are two-tailed paired t-test ***p < 0.001, **p < 0.01, *p < 0.05. Source data are provided as a Source Data file.