We have developed a non-peptide compound, HSP-117, antagonist of the tachykinin NK-1 receptor. Binding of 3H-substance P (SP) to the membranes of IM-9 cells was inhibited by the antagonists HSP-117 and CP-99,994, the inhibitory activity of HSP-117 being about 50-fold that of CP-99,994. The SP-induced firing responses of single neuron activity in slices of the nucleus tractus solitarius of ferrets were inhibited by 10 microM HSP-117. Intracerebroventricular injection of HSP-117 significantly inhibited retching and vomiting induced by copper sulphate and morphine and the inhibitory effect of HSP-117 on emesis was greater than that of CP-99,994. These results indicate that (1) HSP-117 is a potent anti-emetic agent, blocking NK-1 receptors in the nucleus tractus solitarius and (2) NK-1 receptors in the nucleus tractus solitarius play an important role in emesis induced by broad-spectrum emetic stimuli.