Reduction of Na(+) Enhances Phosphoinositide Hydrolysis and Differentiates theStimulatory and Inhibitory Responses to Quisqualate in Rat Brain Slices

摘要

The concentration of Na+ in the incubation medium significantly influencedphosphoinositide hydrolysis induced by some, but not all, agonists in rat cerebral cortical slices. Reductions of the Na+ concentration below 120 mM resulted in incremental increases in basal and norepinephrine-stimulated accumulation of (3H)inositol monophosphate in cortical slices that had been prelabelled with (3H) inositol, and maximal responses were obtained with 0 to 5 mM Na+. In contrast, the responses to carbachol and ibotenate were similar in medium containing 120 or 5 mM Na. In medium with 120 mM Na+, quisqualate has two effects on phosphoinositide hydrolysis in cortical slices, including a relatively weak stimulatory effect and an inhibitory modulation of the stimulation induced by norepinephrine. These two responses to quisqualate were differentially modulated by Na+.