The real world equivalent of forkroot, the plant that drugs channelers, is probably mandrake (Mandragora offcinarum) a dangerous plant with a forked root chock full of alkaloids and the subject of many legends and associations with witches. Forkroot works on men as well as women channelers.
Although his take on Matrim Cauthon in this book is often debated, Brandon Sanderson has said he learned a great deal as an author from the experience. What did you think of Mat in this book?