Substituted 1,4-piperazine-heteroaryl derivatives as 5-HT.sub.1D receptor agonists

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

• ##STR22## wherein Z represents an optionally substituted five-membered heteroaromatic ring selected from furan, thiophene, pyrrole, oxazole, thiazole, isoxazole, isothiazole, imidazole, pyrazole, oxadiazole, thiadiazole, triazole and tetrazole wherein the optional substituents are methyl, ethyl, benzyl or amino;
• E represents a chemical bond or a straight or branched alkylene chain having from 1 to 4 carbon atoms;
• Q represents a straight or branched alkylene chain having from 1 to 6 carbon atoms, optionally substituted in any position by a hydroxy group;
• U represents C--R.sup.2 ;
• V represents N--R.sup.3 ;
• R represents a group of formula --W--R.sup.1 ;
• W represents a carbonyl group (C.dbd.O), or a straight or branched alkylene chain having from 1 to 4 carbon atoms;
• R.sup.1 represents --OR.sup.x, --OCOR.sup.x, --OCONR.sup.x R.sup.y, --NR.sup.x R.sup.y, --NR.sup.z COR.sup.x or --NR.sup.z CONR.sup.x R.sup.y ;
• R.sup.x and R.sup.y independently represent hydrogen, methyl, benzyl, methoxy-benzyl, acetylamino-benzyl, 1-phenylethyl, 2-phenylethyl, 2-hydroxy-1-phenylethyl, 1-(acetylamino-phenyl)ethyl, 2-(acetylaminophenyl )ethyl, 1-hydroxy-3-phenylprop-2-yl, 1-hydroxy-1-phenylprop-2-yl, furylmethyl, thienylmethyl and -pridylmethyl;
• R.sup.a and R.sup.z independently represent hydrogen, methyl or benzyl;
• and
• R.sup.2 and R.sup.3 independently represent hydrogen or C.sub.1-6 alkyl.