Reverse loops do require special wiring. You need to electrically isolate the loops on both routes of the turnouts.
Bachmann sells 'isolated gap' E-Z track with wire connectors underneath:
http://shop.bachmanntrains.com/index.php?main_page=product_info&cPath=879_604_782_783&products_id=2495Or you can use a razor saw to to make your own rail gaps and fill them with styrene to prevent the rails from coming back together and shorting out.
Also, you will need to reverse the polarity of the main line while the train is between the gaps of the reverse loops, this can be done manually or with electronics.
More information is available here:
http://www.azatrax.com/model-railroad-reverse-loop.html