Tricyclic heterocyclic compounds and their use in treating benzodiazepin receptor-related ailments

A heterocyclic compound having the formula I ##STR23## wherein R.sup.3 is ##STR24## wherein R' is C.sub.1-6 -alkyl, C.sub.3-7 -cycloalkyl, or C.sub.1-6 -alkoxymethyl;

• --A-- is --C(.dbd.O)--NR'"--or --NR'"--C(.dbd.O)--
• wherein R'" is C.sub.1-6 -alkyl;
• X is C or N;
• and
• R.sup.4 is hydrogen, halogen, CN, C.sub.1-6 -alkyl, C.sub.2-6 -alkynyl, trimethylsilyl-C.sub.2-6 -alkynyl, aryloxy which may be substituted with halogen, aralkoxy, C.sub.3-7 -cycloalkoxy which may be substituted with one or more C.sub.1-6 -alkyl groups, or NR""R'"", wherein R"" and R'"" independently are C.sub.1-6 -alkyl or together with the nitrogen atom form a piperidine ring, provided that R.sup.4 is not hydrogen, methyl or halogen when A is --C(C.dbd.O)--NR'"-- and R.sup.3 is oxadiazole, R' is C.sub.1-6 -alkyl or C.sub.3-7 -cycloalkyl, and X is C, and that R.sup.4 is not hydrogen, methyl or halogen when A is --NR'"--C(.dbd.O)--R.sup.3 is oxadiazole, and X is C.