Figure 7. Connexin 36 is required for formation of electrical coupling between interneurons in neocortical layer 1.

(a,b,d,e) DIC (a,d) and GFP expression (b,e) images of a quadruple recording of four layer 1 interneurons in a Ctrl-shRNA (a,b) and Cx36-shRNA (d,e) neocortical slice. The red arrows indicate reciprocal electrical coupling (b,e). Scale bar, 20 μm (a,b), 40 μm (d,e). (c,f) Sample traces of voltage changes in the four neurons in response to sequential current injection into one of the four neurons in Ctrl-shRNA slices (c) and Cx36-shRNA slices (f). Green circles indicate GFP⁺ cells, and white circles indicate GFP-negative (GFP⁻) cells. The average traces are shown in individual table cells at varying scales. Scale bar, 3 mV (blue), 70 mV (red), 200 ms (horizontal, black) and 200 pA (vertical, black). ‘Pre-Stimu.', presynaptic stimulus protocol. (g) Summary of the proportion of electrical coupling observed between layer 1 GFP⁺ interneurons in Ctrl-shRNA or Cx36-shRNA slices at P9–P25. Green circles indicate GFP⁺ cells. n=21 mice for Ctrl-shRNA group, 37 mice for Cx36-shRNA group. ***P<0.001, χ²-test, Fisher's exact test.