Is there a message to be listen to when editor enter play mode?

hi,
Im trying to detect the event on editor window when unity editor enter play mode.
I need this because everytime you enter play mode, unity destroy all the scriptableobject that i created, and i want to save this objects to asset then recover them.
I try the OnDestroy() but this message only be received when i close the editor window. What I am doing now is save objects manually before enter the playmode and when the object reference == null, i reload them from asset. which is kind of lame.

When the editor is playing

EditorApplication.isPlaying

will evaluate as true. This might also be useful: http://forum.unity3d.com/threads/155352-Serialization-Best-Practices-Megapost

Reference:

There is now EditorApplication.playModeStateChanged event.