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. 2017 Jul 5;95(1):63–69.e5. doi: 10.1016/j.neuron.2017.06.022

Figure 4.

Figure 4

Inter-synaptic GABAAR Diffusion Shapes Inhibitory Synaptic Currents

(A) Schematic of the GABA uncaging protocol. (1) A single UV laser pulse (0.5 ms, 0.1 mW) is applied at “synapse A” to record a baseline uIPSC. (2) A UV laser train pulse (4 s at 16 Hz) induces synaptic GABAAR desensitization at “synapse B.” (3) A UV laser pulse at “synapse A” monitors the modulation of uIPSC after the desensitizing train at “synapse B.”

(B) Representative traces of uncaging currents recorded in the control (black), during LiGluK2 activation (green), and upon the X-link protocol (red), before (1) and 660 ms after (3) the UV laser train pulse, as described in (A).

(C) Normalized recovery of uIPSC amplitude induced at “synapse A” after the delivery of the UV laser train pulse at “synapse B” (arrow) in the control (black), LiGluK2 (green), and X-link (red). At 660 ms: ctr = 0.71 ± 0.03, n = 12; 11 neurons in 5 cultures; stim = 0.82 ± 0.04, n = 12; 6 neurons in 4 cultures; X-link = 0.91 ± 0.03, n = 14; 9 neurons in 4 cultures; p < 0.05 ctr versus stim, p < 0.001 ctr versus X-link, Mann-Whitney U-test. Data are represented as means ± SEM.

(D) Reconstructed trajectories of GABAARs (blue) in control (left) and upon GABAAR X-link (right). Inhibitory synapses are in gray. Inset: schematic of the X-link protocol.

(E) Model for the modulation of uIPSCs by inter-synaptic lateral diffusion of desensitized GABAARs. Upon sustained inhibitory synaptic activity, the amplitude of synaptic responses at individual synapses is reduced by intruder desensitized GABAARs from neighboring synapses. Impeding GABAAR lateral diffusion prevents such modulation of inhibitory synaptic transmission.