Abstract: The present experiments were designed to investigate the effects of γ-aminobutyricacid(GABA) on isolated dog cerebral arteries(basilar arter). on addition of agonists phenylephrine10μmol·L^-1,5-HT 10μmol·L^-1, or KCl 25 mmol·L^-1, the isometric tension of the contrac-tion increased 0,51±0.18g,0.33±0.12 g and 0.57±0.16g. After GABA at 50μmol·L^-1,the contraction was shown to decrease 0.27±0.15g,0.19±0.07g and 0.17±0.06g,themaximal relaxation were 45.49%±26.4%, 58.60%±12.96%and 27.75%±15.78%,respectively. But it showed no effect on the contraction induced by high concentration of KCl (45mmol·L^-1).GABA also showed a potent relaxation on the contraction induced by cold Krebssolution(T 28±0.5℃). The finding suggest that GABA can inhibit the muscle tone induced byvarious agonists and cooling in isolated dog basilar artery.