If you have dismissed the warning dlog giving you the option to have LR render the image, no...the only other option is to export and then open in Photoshop.
Ok.. I have reset my warning dialogs. I'm using LR 4 (camera raw 7.1) and PS CS 5 with Camera Raw 188.8.131.529
When I go to edit a raw file in PS, I still don't get a warning, It just hands the file off to PS and renders in PS.