Antinociception Caused by the Extract of Hedyosmum brasiliense and its Active Principle, the Sesquiterpene Lactone 13-Hydroxy-8,9-dehydroshizukanolide - Trentin, Ana P; Santos, Adair R S; Guedes, Alessandro; Pizzolatti, Moacir G; Yunes, Rosendo A; Calixto, João B (Planta Medica, 1999)