CakePHP joining Models between two tables, twice

I have a question about how to set up the relations between two models when they join to each other in two different regards.

I'll give an example of the problem I've got:

Users (id, name)
Messages (id, message, from_user_id, to_user_id)

(In my case, it's not users nor messages, but this hopefully illustrates the problem in a simpler way)

Users can send messages to each other, and each Message has a User who sent it and a User who will receive it. I'm trying to figure out the Model relations:

class User extends AppModel {
    var $hasMany = array("Message");

class Message extends AppModel {
    var $belongsTo = array("User");

I'm also not sure how the fields should be named in the database so CakePHP will pick up the relationship properly.