A compound of formula I wherein X 1 and X 2 are N or CH, with the proviso that X 1 and X 2 are not simultaneously N; X 3 is a bond, C 1 -C 4 -alkylene, C 1 -C 4 -haloalkylene or CO; X 4 is N or CH; X 5 is C-R 1 or N; R 1 and R 2, independently of each other, are selected from hydrogen, halogen, cyano, C 1 -C 3 -alkyl, fluorinated C 1 -C 3 -alkyl, C 1 -C 3 -hydroxyalkyl, C 1 -C 3 -alkoxy and fluorinated C 1 -C 3 -alkoxy; R 3 is selected from hydrogen, halogen, cyano, C 1 -C 3 -alkyl, fluorinated C 1 -C 3 -alkyl, C 1 -C 3 -hydroxyalkyl, C 1 -C 3 -alkoxy, fluorinated C 1 -C 3 -alkoxy and hydroxyl; R 4 is selected from C 1 -C 3 -alkoxy; R 5 is selected from hydrogen and C 1 -C 3 -alkoxy; R 6 is selected from cyano and halogen; R 7 is selected from hydrogen, halogen and cyano; R 8 and R 9, independently of each other and independently of each occurrence, are selected from halogen, C 1 -C 4 -alkyl, C 1 -C 4 -haloalkyl, C 1 -C 4 -alkoxy and C 1 -C 4 -haloalkoxy, with the proviso that R 8 and R 9 are not halogen, C 1 -C 4 -alkoxy or C 1 -C 4 -haloalkoxy if they are bound to a carbon atom in α-position to a nitrogen ring atom; or two non-geminal radicals R 8 form together a group -(CH 2) n -, where n is 1, 2, 3 or 4, where 1 or 2 hydrogen atoms in this group may be replaced a methyl group; or two non-geminal radicals R 9 form together a group -(CH 2) n -, where n is 1, 2, 3 or 4, where 1 or 2 hydrogen atoms in this group may be replaced a methyl group; each R 10 is independently selected from halogen, C 1 -C 4 -alkyl and C 1 -C 4 -haloalkyl; a is 0, 1, 2, 3 or 4; b is 0, 1, 2, 3 or 4; and c is 0, 1, 2, 3 or 4; and the N-oxides, stereoisomers and pharmaceutically acceptable salts thereof, and the compound of the formula I, wherein at least one of the atoms has been replaced by its stable, non-radioactive isotope. X 1 and X 2 are N or CH, with the proviso that X 1 and X 2 are not simultaneously N; X 3 is a bond, C 1 -C 4 -alkylene, C 1 -C 4 -haloalkylene or CO; X 4 is N or CH; X 5 is C-R 1 or N; R 1 and R 2, independently of each other, are selected from hydrogen, halogen, cyano, C 1 -C 3 -alkyl, fluorinated C 1 -C 3 -alkyl, C 1 -C 3 -hydroxyalkyl, C 1 -C 3 -alkoxy and fluorinated C 1 -C 3 -alkoxy; R 3 is selected from hydrogen, halogen, cyano, C 1 -C 3 -alkyl, fluorinated C 1 -C 3 -alkyl, C 1 -C 3 -hydroxyalkyl, C 1 -C 3 -alkoxy, fluorinated C 1 -C 3 -alkoxy and hydroxyl; R 4 is selected from C 1 -C 3 -alkoxy; R 5 is selected from hydrogen and C 1 -C 3 -alkoxy; R 6 is selected from cyano and halogen; R 7 is selected from hydrogen, halogen and cyano; R 8 and R 9, independently of each other and independently of each occurrence, are selected from halogen, C 1 -C 4 -alkyl, C 1 -C 4 -haloalkyl, C 1 -C 4 -alkoxy and C 1 -C 4 -haloalkoxy, with the proviso that R 8 and R 9 are not halogen, C 1 -C 4 -alkoxy or C 1 -C 4 -haloalkoxy if they are bound to a carbon atom in α-position to a nitrogen ring atom; or two non-geminal radicals R 8 form together a group -(CH 2) n -, where n is 1, 2, 3 or 4, where 1 or 2 hydrogen atoms in this group may be replaced a methyl group; or two non-geminal radicals R 9 form together a group -(CH 2) n -, where n is 1, 2, 3 or 4, where 1 or 2 hydrogen atoms in this group may be replaced a methyl group; each R 10 is independently selected from halogen, C 1 -C 4 -alkyl and C 1 -C 4 -haloalkyl; a is 0, 1, 2, 3 or 4; b is 0, 1, 2, 3 or 4; and c is 0, 1, 2, 3 or 4;