Sodium dependence of GABA transport in rat hypothalamic synaptosomes.
The sodium dependence of gamma-aminobutyric acid (GABA) uptake has been studied in rat hypothalamic synaptosomes, and the results compared to previous studies in cortical synaptosomes. Initial velocity of GABA uptake was measured as a function of both GABA and sodium concentration, and these data were fitted to the rate equation for each of several plausible models. The minimal best-fit model was found to be identical to that for cortical synaptosomes. However, the constants which quantitate the model were found to differ for hypothalamus and cortex. As a result, uptake at any combination of [Na] and [G] in hypothalamic synaptosomes is approximately double that in cortical synaptosomes. The rate equation for the minimal best-fit model was utilized to define and compute certain parameters which are useful in comparing transport mechanisms (Vmax, Va, Kt, Jm, and k Na). In all cases, differences were found between hypothalamus and cortex.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D012964:Sodium / Q000494:pharmacology*; D013574:Synaptosomes / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005680:gamma-Aminobutyric Acid; D012964:Sodium