GABA ((-aminobutyric acid) is the brain's main inhibitory neurotransmitter. The highest level of GABA is found in the CNS. GABA presence and GAD (the key enzyme in GABA synthesis) activity were also detected in several non-neural tissues. We observed an increase in the GABA level and GAD activity in tumor tissues in comparison with normal tissue. Our study examined the GABA content and GADactivity in the normal mammary gland of healthy mice and in the 16/C adenocarcinoma mammary gland as an experimental model. Comparison between and within groups were made by one way analysis of variance (ANOVA). Our investigations demonstrated GABA presence and GAD activity in the normal mouse mammary gland tissue. We observed a significant increase in the GABA level and GAD activity in mouse 16/C mammary cancer cells in comparison with normal mammary gland skin. Tumor tissues showed a clear positive correlation between GABA levels and GAD activity. There were no significant differences in the GABA content and GAD activity between mammary gland skin coming from tumor bearing and healthy mice. An increase of the GABA level and GAD activity in tumor tissues could possibly reflect a local antitumor response, however, hypoxia of tumor cells could also be considered. The observed GABA metabolism pathway in mammary cancer compared with literature data concerning other tumors, can suggest the possibility of therapeutic usefulness of GABA-ergic system agonists such as baclophen.

Keywords: Neoplasms, breast cancer, GABA, GAD