Novel N-substituted azaheterocyclic carboxylic acids and esters thereof in which a substituted alkyl chain forms part of the N-substituent, the compounds thus having the general formula I ##STR1## wherein Y is ##STR2## wherein R.sup.1 and R.sup.2 independently are C.sub.3-8 cycloalkyl phenyl or thienyl all of which may be optionally substituted with halogen, trifluoromethyl, C.sub.1-16 alkyl or C.sub.1-6 alkoxy; s is 1, 2 or 3; x is --CH.sub.2 --, --O-- or ##STR3## -wherein R.sup.3 is hydrogen or C.sub.1-6 -alkyl; r is 2, 3 or 4; R.sup.4 and R.sup.5 each represents hydrogen or may together represent a bond and R.sup.6 is OH or C.sub.1-8 -alkoxy; and pharmaceutically acceptable acid addition salts are potent inhibitors of GABA uptake from the synaptic cleft.