Temporal profile of interaction between glutamatergic and GABAergic synaptic activity.

(A) On-path phasic GABAergic activity is delivered to a dendrite positioned more proximally on the same path to the soma as the dendrite receiving glutamatergic synaptic input. As before, synaptic potentials are illustrated at (B) dendritic site of glutamatergic activity and (C) cell soma. L-glutamate mediated excitation alone (15 neighboring spines activated at 1 ms intervals along the chosen dendrite; black trace), phasic GABAergic stimulation alone (3 simultaneous synaptic stimulations delivered 4 times at an interval of 1 ms to the proximal on-path dendritic site giving a total of 12 GABA synapses activated; light gray) and the effect of varying glutamatergic stimulation at temporal intervals relative to this fixed GABAergic input described (blue to orange illustrate 5 traces with Δt = tGLUT−tGABA in the range of −10 to 30 ms, respectively, at 10 ms intervals) are illustrated. The absolute amplitude of the synaptic potential in the dendrite was measured in the absence of GABAergic activity (P1) or either relative to the amplitude of the underlying depolarizing phasic GABAergic potential response (P2) or relative to the underlying baseline (P3). (D) and (E) show the supralinear effect of varying glutamatergic spine activation relative to a fixed distal off-path GABA synaptic input on P2 and P3 normalized to P1, respectively. For comparison, data from the off-path distally located phasic GABAergic activity is overlayed (D and E). The widened temporal window for supralinear summation in this simulation arises from the reduced path length from the site of GABA activation to the site of glutamatergic clustered activity which manifests as an increase in magnitude of GABAergic PSP at this location (e.g., compare GABAergic PSPs; light gray trace in panel B to its equivalent in Fig 6G). The data underlying the graphs shown in the figure can be found in dx.doi.org/10.5281/zenodo.10387118. (EPS)