[Neuroscience] Re: Can a single neuron release multiple neurotransmitters?

[Matthew Kirkcaldie]

In article <Xns98ACD75D841C5polyfractalgmailcom At 66.250.146.128>,
 Zachary Tong <polyfractal At gmail.com> wrote:

> I was curious if single neurons have the ability to release multiple 
> neurotransmitters, or if each neuron was limited to one specific 
> transmitter.  If they can have multiple transmitters, how is it decided 
> which transmitter is released?  Are they all dumped into the synapse at the 
> same time?  My understanding is that vesicles are sensitive to calcium ion 
> levels and will release their transmitters when the concentration reaches a 
> certain point.  This seems that if there are multiple types of 
> transmitters, the vesicles would release them all at the same time.
> 
> Thanks,
> -Zachary Tong

During development it's been shown that neurons which release glycine in 
the adult, "work up to it" by releasing GABA and glutamate at earlier 
stages, and in fact developing neurons in the auditory brainstem nuclei 
will release glutamate, GABA and glycine all at the same synapse, in 
separate vesicles (Gillespie et al., Nature, 2005).

I doubt there would be a way to select between the transmitters for 
release - after all an action potential is an action potential.  However 
I could imagine that secondary transmitters leaking back across the 
synaptic cleft could influence the releasability of presynaptic vesicles 
of different kinds.  That's just a guess though.

I believe it's pretty normal for synapses to release transmitters and 
co-transmitters at the same time - nitric oxide being the classic 
example.  The kinetics of each transmitter differ and so releasing 
several kinds would allow different temporal firing patterns to have 
different effects on the synapse.  Seems potentially useful to me.

Hope that helps.

      Cheers,

         Matthew.