1. Electrical Synapses Or Shemesh March 2010 shemesh72369@gmail.com

2. Relatively non-specific. Molecular movement through passive diffusion. Selectivity based upon molecular size (- allow movement of molecules whose molecular weight <1000Da.) (- allow movement of molecules whose diameter < 1.2nm.) Cell #1 Cell #2 Gap junctions

3. Structural arrangement of Gap junctions Connexin Connexon ( A hemi-channel)

4. Structural arrangement of Gap junctions Two docked connexons (a gap junction channel) Gap junction plaque

6. Electric synapses vs. Chemical synapses Electric synapses vs. Chemical synapses Synaptic delay No delay0.2ms-2ms Direction of conductance Bi- directional, but not necessarily symmetric unidirectional

7. Two coupled cells in Vitro Cell 2 Cell 1

8. I2I2I2I2 I1I1I1I1 The equivalent electrical circuit r1r1 rcrc r2r2 Cell 2Cell 1 V1 V2

9. The equivalent electrical circuit V1 I2I1 V2 r1r1 rcrc r2r2 Cell 2Cell 1 V1 V2

10. Basic concepts I 1, I 2 V 11, V 22, V 21, V 12 V 1 1 Voltage in cell Current injected to cell r1r1 rcrc r2r2 Cell 2 Cell 1V1V2

11. Input resistances r1r1 rcrc r2r2 Cell 2 Cell 1

12. Input resistances If r c << r 2 and r c << r 1 Then r1r1 rcrc r2r2 Cell 2 Cell 1

13. Transfer resistances r1r1 rcrc r2r2 Cell 2 Cell 1 r1r1 rcrc r2r2 Cell 2 Cell 1

14. Cell 2 Cell 1 Cell 2 Cell 1 Coupling coefficients Potential in un-injected cell Potential in injected cell

15. A typical trace I1 V11V12 V21 V22 I2

16. Cell 2 Cell 1 Traces! 0 0.5 1.0 1.5 2.0 -0.5 nA, injected to cell 2 (left cell). Cell1 Cell2

17. Cell 2 Cell 1 -0.5 nA, injected to cell 1 (right cell). Traces! Cell1 Cell2

18. Cell 2 Cell 1 Cell1 Cell2 Traces! +0.4 nA, injected to cell 2 (left cell).

19. Cell 2 Cell 1 accommodation summation Traces! +0.4 nA, injected to cell 2 (left cell). Cell1 Cell2