Don't allow them to play like that? Start correcting and separating when you see the playing is getting too rough. Give them a break from each other, if even for a minute and you'll see that they don't escalate as fast. I wouldn't let them play off leash until you have this issue fixed.
If you start correcting for playing at the neck...they will realize it at some point and stop. The issue is stemming from the fact that your 10 month old doesn't know how to play properly and isn't correcting the younger one safely. So at this point you need to teach them both how to play. Just don't let it get that rough and when you notice things escalating break them apart and do something else to get their attention off of each other.
CD RE TC HIC 7/10