Figure 2: Electrical and GABAergic connections between layer 1 interneurons.
From: Electrical coupling regulates layer 1 interneuron microcircuit formation in the neocortex
(a) Representative traces of voltage responses to 500 ms current pulse step injections recorded in the current-clamp mode. The red traces show the initial AP spike. Layer 1 interneurons were divided into two subtypes, LS and BS neurons, based on their AP firing patterns. The inset shows the ADP in the initial AP of a BS neuron. (b) Histogram showing that the majority of interneurons displayed LS firing pattern (LS, 79.7%, 374 cells; BS, 20.3%, 95 cells; n=63 mice). (c) Summary of the proportion of electrical coupling observed between layer 1 interneurons at P9–P25. The rate of electrical connections between LS interneurons is significantly higher than the rate between LS and BS interneurons and between BS interneurons. (d) The scatter plot of coupling coefficients revealed no significant difference between interneuron subtypes (LS–LS pairs, 1.8±0.12%, n=122; LS–BS pairs, 2.2±0.45%, n=22; BS–BS pairs, 1.1±0.15%, n=4). (e) Summary of the proportion of GABAergic connections between interneuron subtypes. (f) The unidirectional chemical synapses between LS and BS interneurons showed directional selectivity. (g) The amplitude of uIPSCs between LS interneuron pairs (37.98±2.13 pA, n=73) was significantly larger than those between LS–BS pairs (24.22±2.09 pA, n=39) and BS–BS pairs (21.44±1.73 pA, n=34) (not including failures). *P<0.05, **P<0.01, ***P<0.001, n.s., P>0.05, not significant. χ2-test, Fisher’s exact test and Mann–Whitney rank sum test. Error bars in d and g represent mean±s.e.m. ADP, after depolarization.
