Check out this article on Belladonna/Bush. Looks like there's a lot we don't know.
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=10863712&dopt=Abstract
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=10863712&dopt=Abstract