Differential role of pre- and postsynaptic neurons in the activity-dependent control of synaptic strengths across dendrites
Fig 2
Postsynaptic strengths segregate depending on dendritic branches and locally, on presynaptic inputs.
(A) Triple recording scheme with two independent presynaptic neurons forming convergent inputs onto a postsynaptic neuron. (B) Example traces of aEPSCs recorded in Sr2+-containing aCSF in response to stimulating each of the two convergent inputs. (C) Comparison of average aEPSC amplitude of two inputs (R2 = 0.95, p < 0.0001, n = 8 triplets). Linear regression and 95% confidence interval (gray) are shown. (D) Histograms from a representative triple recording experiment showing quantal event amplitudes for each of the two convergent inputs (gray and white bars). (E) Comparison of mean aEPSC frequency of two convergent inputs shows no correlation (R2 = 0.083, p = 0.4885, n = 8 triplets). (F) Scheme to probe the distribution of surface AMPA receptors. A postsynaptic neuron expresses SEP-GluA1 or SEP-GluA2 (yellow), and a nearby presynaptic partner is filled with an Alexa Fluor dye (blue). (G) Fluorescence images from a representative experiment. Left, postsynaptic SEP-GluA1–positive dendrites are contacted by an Alexa Fluor dye–labeled axon; some SEP-GluA1 puncta are contacted by the labeled axon (filled arrowheads), and others are presumed to receive synaptic inputs from unlabeled axons (open arrowheads). Right, same view shows punctate SEP-GluA1 signal representing putative postsynapses whose fluorescence intensity is color-coded. Scale bar, 10 μm. (H) Summary graph of the fluorescence intensity difference for pairs of SEP-GluA1 (left) or SEP-GluA2 (right) puncta apposed to different or same axon and belonging to different or same dendrites (SEP-GluA1: n = 461 puncta from 8 cells, SEP-GluA2: n = 1,066 puncta from 9 cells, one-way ANOVA followed by Tukey multiple comparison test, **p < 0.01, ***p < 0.001). Underlying data can be found in S1 Data. aCSF, artificial cerebrospinal fluid; aEPSC, asynchronous EPSC; EPSC, excitatory postsynaptic current; AMPA, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; GluA, AMPA receptor subunit; Rec, recording pipette; SEP, superecliptic pHluorin.