Histamine h3 receptor ligands

Compounds of formula (I) (and pharmaceutically acceptable salts thereof) are histamine H3 receptor ligands. A in the formula represents (CH2)m, m being from 1 to 3; B is (CH2)n, n being from 1 to 3; x is from 0 to 2; R is C1 to C10 hydrocarbyl, in which up to 2 carbon atoms may be replaced by O, S or N; and up to 2 hydrogen atoms may be replaced by halogen; R is H or C1 to C15 hydrocarbyl, in which up to 3 carbon atoms may be replaced by O, S or N, and up to 3 hydrogen atoms may be replaced by halogen; R is absent when -Y-Z-R2 is attached to W, or is H or C1 to C7 hydrocarbyl when -Y-Z-R is not attached to W; W is nitrogen; X is -CH2-, -O- or -NR -, R being H or C1 to C3 alkyl; Y replaces a hydrogen atom on any of A, B, W and X, and is C2 to C10 alkylene, in which one non-terminal carbon atom may be replaced by O; and Z is (II), (III), (IV), (V), (VI), or (VII) wherein R , R and R are independently H or C1 to C15 hydrocarbyl, in which up to 3 carbon atoms may be replaced by O or N, and up to 3 hydrogen atoms may be replaced by halogen, and Q is H or methyl, or Q is linked to R or R to form a five-membered ring or Q is linked to R to form a six-membered ring