The present application relates to indole and indoline derivatives of formula (I), (II), (III), (IV), (V), or (VI) ##STR00001## wherein a, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, U, V, W, X, Y, and Z are as defined in the specification. The present application also relates to compositions comprising such compounds, and methods of treating disease conditions using such compounds and compositions, and methods for identifying such compounds.