It varies...
I did a run of DNP a few months ago and to be honest, I didn't experience much of a rebound at all... anabolic or otherwise. I think it depends on the person but the rebound is said to begin roughly 3-4 days after finishing up your dnp cycle. It takes that long for most of the chemical to work its way out of your system.
Also, the rebound may be influenced by how/when you replenish your glycogen stores. A lot of people advise to keep carbs and fats relatively low during a dnp run and then have a carb-up day after you've finished in order to get glycogen back to normal. I believe that if you have any kind of rebound, it'll be closely related to when and how you choose to have that 'carb day'.
Hope this helps.
- Judoman