Patients' antibodies reversibly reduce synaptic NMDA receptor clusters without affecting the number of synapses. a , Hippocampal neurons immunostained for total NMDAR clusters, a presynaptic glutamatergic terminal protein, VGlut, and a postsynaptic protein localized to glutamatergic synapses, PSD-95. Treatment with patient CSF for 3 d reduces the density of synaptic NMDAR clusters without affecting the number of excitatory synapses. After removal of patient CSF, the proportion of NMDAR clusters localized to synapses returns to baseline. Scale bar, 5 μm. b , Colocalization of presynaptic and postsynaptic proteins at excitatory synapses (n = 36 cells, 3 independent experiments; 2 patient, 1 control samples). c , NMDAR cluster density at excitatory synapses (synaptic NR1). The asterisk indicates significant difference (one-way ANOVA test followed by Bonferroni's multiple comparison test, p < 0.001). Error bars indicate SEM.