What the purpose of using trypsin, collagenase and DNase with dissociated neurons?

Question

for neuron culture in electrophysiology

Answer 1

Neurons are originally embedded in a tight extracellular matrix composed of a variety of cells. If you want to study one neuron, you need to disassociate it from the remainder of the tissue. Experiments with a variety of enzyme have found those three to be the most effective at producing that dissociation. Which is not too surprising really, given their individual activities:

Trypsin helps cells be less intrinsically sticky, so to speak. It is sometimes used alone to remove cells that are adhering to petri dishes and the like. Collagenase breaks down the major fibrous component of connective tissues between cells. The severed collagen fibers then usually unwind and break down on their own. DNase destroys DNA that it's exposed to, of course. It is useful for separating cell clumps as well.

So you can see how they would be very useful to produce a dissociated neuron in the first place! By the same token, since (usually) you're taking care to preserve many of the properties of the original cells, if you leave them be for a time they may very well become sticky, collageny, and clumpy again, so additional treatments might be appropriate as well. Hope that helps!