Can iMac act as 2nd Monitor for MacBook Pro?

I currently have an older 2GB iMac (still running OSX) that I use primarily for photographic processing (Photoshop, Bridge). I would very much like to get a new 15" MacBook Pro for the same plus portability. Here at home, I would like to be able to run my old iMac as a monitor only (bigger screen) for the Pro? Is that possible?

Thanks very much.

I do not think that it is possible as it is a computer not a "dumb" monitor. It has an operating system.. think of it as another laptop with out a lid.

I agree, the iMac has a video OUT, not a video IN, so no love...