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[Neuroscience] Re: Electrical Synapses..

Matthew Kirkcaldie m.kirkcaldie at removethis.unsw.edu.au
Fri Mar 3 06:13:21 EST 2006


In article 
<440787c2$0$21898$5a62ac22 at per-qv1-newsreader-01.iinet.net.au>,
 jason <jkrah_dot_geo_ at yahoo_dot.com> wrote:

> Thanks Matthew for your response also.. Im starting to think this may be 
> an area (importance of elec synapse) of debate in coming years..

Yeah, me too - I remember my surprise when a friend told me about this 
field, I'd always been told that gap junctions were only present in the 
juvenile brain.

> The other day I read (and please remember I am really a beginner) that 
> GapJuncions (ie elect synapse) can potentially also allow the transfer 
> of larger molecules ie transmitters / 2nd Messenger molecules etc..
> Surely this also had some huge potential for the (long term)  modulation 
> of cells..

Yes, I think there is some good evidence that calcium dynamics in cells 
(storage and release from internal stores) can be coupled this way.  
Particularly in heart muscle, but quite possibly in neurons as well.

> The thing I find really interesting (and complex) is the Integrative 
> functions of these gap junctions.. reading about the Leech S-Cell 
> network (& effects of 5ht in learning) - it seems that when a group of 
> cells is tightly coupled by gap-junctions - they can be thought of 
> effectively  one-big-cell.. now if massive connected area of cells exist 
> (eg cortex) - can these also be considered to be acting like single 
> neural entities ???

I'd guess it would be more like a group modulation - as a whole the 
group of cells tends to respond more to particular types of inputs 
because of the collective influence.  I'd also point out that a gap 
junction is not susceptible to competitive binding or modulation like 
chemical synapses - which may provide a sort of reference for the rest 
of the brain's dynamics.

For 5-HT in learning I'd check out some of the insane things coming from 
Kandel's lab these days (I think the papers are Si et al from 2003 or 
so).  I reckon single synapses may prove more complex than people 
thought the whole brain was 50 years ago!

> on a side note - I read about the ability of a axonal branch to delay 
> and then reflect a AP back up the main axon the other day.. Im starting 
> to think that in Neurobio - if soemthing is remotely physically possible 
> .. then its probably happening somewhere.. I love this stuff..

Me too.  If you haven't, have a look at Greg Stuart and Michael 
Hausser's work on dendritic processing.  And there was a great paper a 
few years ago about how signals get shunted in dendrites according to 
the pattern of stimulation, so that in some circumstances dendrites get 
"functionally amputated" and the functional anatomy reconfigures 
dynamically according to the inputs.  Makes your head spin.

> Thanks again for you feedback guys!!! .. I feel priveiged to be able to 
> ask these things to poeple 'in the know'..

I'd have to assume you're referring to Prof Norman there, my knowledge 
has a way to go before I reach his level.  But I share his (and your) 
enthusiasm.

      Cheers, MK.


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