Imidazo-pyridine derivatives as ligands for GABA receptors

A compound of formula I, or a pharmaceutically acceptable salt or a prodrug thereof:

• wherein
• Y represents a chemical bond, or a methylene (CH2), carbonyl (C═O), thiocarbonyl (C═S) or amide (CONH or NHCO) linkage;
• Z represents an optionally substituted phenyl, heteroaryl or heteroaryl(C1-6)alkyl group, wherein heteroaryl is selected from the group consisting of pyridine, pyrrolidine, imidazole and thiophene, or a group of formula —NR1R2;
• R1 and R2 independently represent hydrogen, hydrocarbon or a heterocyclic group wherein the heterocyclic group is selected from the group consisting of pyridine, pyrrolidine, imidazole and thiophene;
• or R1 and R2, together with the intervening nitrogen atom, represent an optionally substituted heterocyclic ring selected from azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl and thiomorpholinyl;
• and
• R3 represents phenyl or furanyl, which groups may be optionally substituted.