Effects of GABA on lung function in asthmatics after methacholine inhalation

Central inhibitory effects of GABA (Gamma-Aminobutyric acid) are partly investigated and they result in reduced neurogenic extravasation and anticholinergic bronchoconstriction. The aim of the study was to determine the GABA effect on airways passage in patients with bronchial asthma. Study of subjects with well-controlled asthma included: spirometry as well as methacholine bronchoprovocation testing, prior and after GABA inhalation. Bronchial reactivity index was calculated as percentage change index (I%C). On day 1, a group of 12 subjects was treated with incremental methacholine aerosol doses. While FEV being decreased for at least 20% of the initial value, spirometry variables were measured immediately after inhalation, and then after 7, 15 and 30 minutes. On day 2, upon registering initial values and introducing inhaled GABA of 300 mcg/ml for 10 minutes, the identical bronchoprovocation test was done. The obtained values were compared by means of Student’s t-test. Upon GABA inhalation, methacholine showed no statistically significant changes in tested variables values (p>0.05). After inhaled GABA, I%C proved significantly reduced and more equable. In conclusion, the obtained results showed that bronchoconstrictive response to methacholine was significantly decreased after GABA inhalation and that GABA proved significant inhibitory effect in asthma patients.