Definition of "lit up"

You wondered what she would be like when she was lit up. Excited, I mean; not tight.

1998, Josephine Tey, The Franchise Affair, page 97

I don't know if Bob remembers the whole thing either; he was pretty lit up.

2005, Jim Greer, James Greer, Steven Soderbergh, Guided by Voices: a brief history

Her thin, pretty face was lit up with an ancient sort of rage.

2010, Jeff Somners, The Terminal State