# [Neuroscience] Re: The relationship between gap junction conductance and coupling coefficient?

Bill.Connelly via neur-sci%40net.bio.net (by connelly.bill from gmail.com)
Thu Jul 2 21:47:14 EST 2009

```I knew it would be something simple like that.

Thank you very much, it fits perfectly with what I have measured.

On Jul 2, 11:20 pm, r norman <r_s_nor... from comcast.net> wrote:
> On Wed, 1 Jul 2009 20:44:31 -0700 (PDT), Bill
>
>
>
> <connelly.b... from gmail.com> wrote:
> >Does anyone know the relationship between gap junction conductance and
> >coupling coefficient?
>
> >Coupling coefficient is the ratio of the voltage change in cell2 over
> >the voltage change in cell1, when current is injected into cell1.
>
> >I can see the circuit: Two resistors to ground (Rm of cell 1 and 2),
> >linked by the resistance of the gap junction. I can see that as the
> >resistance of the gap junction drops to 0, the coupling coefficient
> >goes to 1 (Assuming the membrane resistance of the two cells is
> >(close) equal, which is a fiar assumption). I can also see, the
> >coupling coefficient goes to 0 when there is no coupling between the
> >cells.
>
> >But is it possible to convert the coupling coefficent to a gap
> >junction conductance?
>
> The coupling coefficient is simply Rm2/(Rg + Rm2), the membrane
> resistance  of cells 2 divided by the total of the gap resistance and
> the membrane resistance.  If you know Rm2 you can do what you ask
> since the junction conductance is simply 1/Rg.  If you don't know it,
> you can't.

```