The Effects of the GABA Agonist Muscimol upon Blood Flow in Different Vascular Territories of the Rat Cortex

Local cerebral blood flow was measured in five regions of rat cortex immediately following intravenous administration of the γ-aminobutyric acid (GABA) agonist muscimol. In contrast to recent observations, no increases in blood flow were found at either of the two time points analysed, and the data revealed that decreases in blood flow previously reported 30 min after muscimol treatment were in evidence as early as 30 s. These results are totally consistent with the conclusion that the overall effects of GABA agonists in the intact animal are to reduce blood flow in line with reduced metabolic demand in the neuropil. However, the heterogeneity of the reductions in cortical blood flow found here possibly suggests a biological role for vascular GABA systems in providing a mitigating influence on fluctuating tissue perfusion.