It's evident that Bowie, at the time, had a little yen for a good ole cowboy type song. He had one on Hunky Dory too ( Eight Line Poem ) and Space Oddity also ( Janine ). Oh, and I do love that "WOO WOO WOO .. " at the beginning of that song!
Sounds like Credence to me, but in all seriousness I believe it's Bowie's little tongue-in-cheek ode to the Rolling Stones. Just listen to the part where he sings "satisfaction, satisfaction" hehe... I can even PICTURE Mick during that part!
Also, I read that he wanted to put another song on the album instead - can't remember which one now, maybe Velvet Goldmine or Sweet Head? In any case, the rejected song contained lyrics that were deemed too sexually overt to put on the album. ;)