(1-[6-([17b-3-Methoxyestra-1,3,5 (10)-trien-17-yl]amino)hexyl]-2,5-pyrrolidine-dione)Inactive analog of U73122 which is used as a negative control.Ref.: 1. Smith, R.J., et al., J. Pharmacol. Exp. Ther., 253: 688, (1990). 2. Bleasdale, J.E., et al., ibid., 255: 756, (1990).