Preadaptations

[porchrat]

There are different kinds of sodium channels. E.g. ligand-gated and voltage-gated. I think they are referring to the voltage-gated ones which are associated with the nervous system.
The research article: Evolution of sodium channels predates the origin of nervous systems in animals
Abstract:

Ah now THAT makes more sense. I thought they were referring to sodium channels in general. That would include things like the transmembranous active sodium channels that set up the sodium concentration gradient in the first place. Surprise at those existing long before nervous systems seemed silly.

Thanks for clearing that up I will give that article a read