Q: Can I access directly the content within the Loader component ?

A: The loader component has a property called content. This will give you a reference the Loader class instance that loaded the content. This means that you can get access to the elements found in the content (like variables, functions, movie clips) and you can event start or stop playing an animation.

Start an animation: myLoader.content.contentLoaderInfo.content.play();
Stop an animation: myLoader.content.contentLoaderInfo.content.stop();
Call a function defined in the content clip: myLoader.content.contentLoaderInfo.content.myFunction();

The attached example uses the loader to load an animation that has a function defined in it.
Files: LoaderAccessContent_AS3.zip