A IHC scores of the expression of NPCT in brain regions or nuclei. The higher IHC scores indicate the more intensive expression of NPCT. B The distribution of NPCT in brain regions activated at the initiation of SE. Bar scale = 100 μm. C Panorama showing the colocalization of NPCT with the neuronal marker NeuN in different territories of the rat hippocampus under physiological condition. (c1-c4) Enlarged pictures of insets from (C). Note that NPCT exists in neuronal somata (asterisks) and proximal dendrites (arrowheads). D The proportions of neurons, astrocytes, and microglia that express NPCT in the hippocampus. E Colocalization of NPCT and postsynaptic marker PSD-95 in the radiatum layer of CA1 and stratum lucidum of CA3. Arrowheads and dotted lines in enlarged pictures indicate the enrichment of NPCT in postsynaptic domain. F Colocalization of NPCT and presynaptic marker synapsin in the radiatum layer of CA1 and stratum lucidum of CA3. Arrowheads and dotted lines in enlarged pictures indicate the localization of NPCT in presynaptic domain. G, H Representative immunoelectron microscopic images showing the synaptic distribution of NPCT in CA1 (G) and CA3 (H). Synapses in (G, H) were classified into four categories based on the distribution of NPCT: NPCT in presynaptic domain (dark blue), NPCT in postsynaptic domain (light blue), NPCT in both pre- and postsynaptic domains (green), synapse without NPCT distribution (orange). Quantitative analysis demonstrated that in CA1 20.13% synapses contained NPCT in presynaptic domain, 32.89% synapses contained NPCT in postsynaptic domain, 10.74% synapses contained NPCT both pre- and postsynaptically, while 36.24% synapses had no NPCT immunoreactivity (n = 149 synapses from 3 rats), while the proportions in CA3 were 8.77%, 43.27%, 12.87%, and 35.09%, respectively (n = 171 synapses from 3 rats). All data are presented as mean ± SEM. n = 3 rats. CA1 field CA1 of the hippocampus, CA2 field CA2 of the hippocampus, CA3 field CA3 of the hippocampus, Ent entorhinal cortex, GrDG granular layer of the dentate gyrus, IHC immunohistochemistry, LMol lacunosum moleculare layer of the hippocampus, MoDG molecular layer of the dentate gyrus, Or oriens layer of the hippocampus, PoDG polymorph layer of the dentate gyrus, Py pyramidal cell layer of the hippocampus, Rad radiatum layer of the hippocampus, SLu stratum lucidum of the hippocampus, Other abbreviations please refer to Supplementary Fig. S1.