Use of GABA

1. A method for inhibiting or treating cough, comprising administering to a subject in need thereof a pharmaceutically and pharmacologically effective amount of a compound of formula (I)

as well as a pharmaceutically acceptable salt, a solvate or an optical isomer thereof, wherein

R 1 represents a hydroxy group, a halogen or an oxo group.

2. The method according to claim 1 , wherein said halogen is fluorine.

3. The method according to claim 1 , wherein the cough is chronic cough.

4. A method for inhibiting or treating cough, comprising administering to a subject in need thereof a pharmaceutically and pharmacologically effective amount of a compound of formula (II)

as well as a pharmaceutically acceptable salt, a solvate or an optical isomer thereof, wherein

R 2 represents hydrogen, a hydroxy group, C 1 -C 7 alkyl, C 1 -C 7 alkoxy or halogen;

R 3 represents hydrogen, C 1 -C 7 alkyl (optionally substituted with hydroxy, mercapto, C 1 -C 7 alkoxy, C 1 -C 7 thioalkoxy, aryl or heteroaryl), aryl or heteroaryl;

with the proviso that R 2 and R 3 are not hydrogen at the same time.

5. The method according to claim 4 , wherein the cough is chronic cough.

6. A method for inhibiting or treating cough, comprising administering to a subject in need thereof a pharmaceutically and pharmacologically effective amount of a compound of formula (III)

as well as a pharmaceutically acceptable salt, a solvate or an optical isomer thereof, wherein

R 4 represents hydrogen, hydroxy group or halogen;

R 5 represents hydrogen, hydroxy group, mercapto, halogen, or an oxo group;

R 6 represents hydrogen or C 1 -C 7 alkyl (optionally substituted with hydroxy, mercapto, C 1 -C 7 alkoxy, C 1 -C 7 thioalkoxy, aryl or heteroaryl), aryl or heteroaryl.

7. The method according to claim 6 , wherein the cough is chronic chough.