Effect of intraventricular gamma-aminobutyric acid (GABA) on discrimination learning in rats.

Rats were trained to perform light-dark discrimination learning for a period of 6 consecutive days. GABA, an inhibitory transmitter, was administered into the lateral ventricle either immediately or 60 min after the completion of each training session. GABA, in dose levels of 100 and 150 microgram and injected immediately after the completion of the session, significantly increased correct responses in comparison with the corresponding control group, while 200 microgram of the drug had no further effect on the correct responses. When the administration of the drug was delayed by 60 min, neither 100 nor 150 microgram of GABA significantly increased correct response. Intraventricular GABA did not affect total activity or water intake which could be considered indexes corresponding to motility and motivational state, respectively. It was concluded that under these conditions GABA improves discrimination learning by its action as an inhibitory transmitter.