Derivatives of 4-amino 3-carboxy naphthyridines and their pharmaceutical compositions

Compounds represented by the general formula in which R1 and R2 are independently selected from hydrogen, C1-C6 alkyl, phenyl or benzyl, or R1 and R2 may form together with the nitrogen atom to which they are attached a C4-C8 saturated heterocycle, R3 and R4 are independently selected from hydrogen or C hd 1-C6 alkyl, R5 is selected from hydrogen or halogen, or C1-C4 alkyl, C1-C hd 4 alkoxy, nitro or trifluoromethyl, n is 1, 2 or 3, and one of the symbols A, B, C or D represents N and the others represent CH, as well as the N-oxids and the the pharmaceutically acceptable acid addition salts and their salts with bases. The compounds have nervous system affecting properties.