Reviewer #1 (Public review): Single molecule counting detects low-copy glycine receptors in hippocampal and striatal synapses

The study presents convincing quantitative evidence, supported by appropriate negative controls, for the presence of low-abundance glycine receptors (GlyRs) within inhibitory synapses in telencephalic regions of the mouse brain.Using sensitive single-molecule localization microscopy of endogenously tagged GlyRs, the authors reveal previously undetected populations of these receptors.Although the functional significance of these low-abundance GlyRs remains to be established, the findings offer valuable insights and methodologies that will be of interest to neuroscientists studying inhibitory synapse biology.