Compounds of formula (I) 1
wherein R.sub.1 or R.sub.2 is a tricyclic or bicyclic ring, each of which
contains at least two heteroatoms, and R.sub.1, R.sub.2, R.sub.3,
R.sub.3a, R.sub.3b, R.sub.4, R.sub.5, L, X, X', Y, Y', Z, and Z' are as
defined herein, are useful in treating conditions or disorders prevented
by or ameliorated by histamine-3 receptor ligands. Also disclosed are
pharmaceutical compositions comprising the histamine-3 receptor ligands,
methods for using such compounds and compositions, and a process for
preparing compounds within the scope of formula (I).