Hi Pavithra,

I don't think there's a single definition of what maturity means in terms of cultures - it's a loose term that depends on context. If one is interested in neuronal morphology, then a mature neuron is one that has elaborated its processes and has "stabilized" its neuronal arbour. If one is interested in functional synapses, then they mean cultures that have reached a stable level of functional synaptic activity (stable frequency of synaptic inputs for example).

As far as neurons "synapsing" with other cell types, that again depends on what you are specifically interested in...I would hazard a guess that in a dense neuronal co-culture with other cell types they will come in contact in some way shape or form, but if your interest is specifically in functional synapses (ie neuronal pre-synaptic terminals that harbour neurotransmitter filled vesicles), for that to happen, the other cell types need to express synaptic molecules such as neuroligins. For further information on this you should look into the work of Ann Marie Craig from the University of British Columbia in Canada, example:

Graf E, Zhang X, Jin SX, Linhoff M, Craig AM. 2004. Neurexins induce differentiation of GABA and glutamate postsynaptic specializations via neuroligins. Cell 119:1013-26.

Best,

Haider

Thanks, Haider, for your time and insights. That's very helpful. 

I study the cell biology of viral infection of neurons.  I don't know that functional synapses or neuronal maturity plays a role in infection. I will read further.

@Haider: On another note, in a pure neuronal cultures (of cortical neurons), will axons form active synapses with neighboring neurons. More specifically, if I isolate the axons in a microfluidic chamber away from the neuronal soma, can  axons synapse on to other axons, or they can synapse only on to other soma/dendrites? 

Thanks in advance for your response.

Hi Pavithra,

What I understood from you is that you are asking about the occurrence of axo-axonic synapses; that's a normal feature of the in vivo nervous system, especially of certain sub-types of inhibitory/GABAergic cells. To what extent those types of synapses are represented in in vitro culture, and specifically in a micro-fluidic environment, I do not know. Irrespective of those "naturally" occurring types of synapses, I believe that generally neuronal cultures are widely regarded to have a greater tendency to form aberrant synapses, so I imagine it's quite possible that there will be at least some functional synaptic connectivity among the axons.

Hope that helps,

Haider

Thanks so much, Haider!