Pharmacological characterization of endogenous acetylcholine release from primary septal cultures

A detailed investigation of endogenous acetylcholine (ACh) release from pri mary embryonic septal cultures is described in this study. Applications of veratridine (25 mu M) or increasing extracellular concentrations of K+ (6-1 00 mM) induced robust increases of endogenous ACh release (similar to 500-1 5,000 fmol/well/10 min). Release stimulated with K+ (25 mM) was sustainable and did not differ significantly over 180 min. ACh release was dependent o n extracellular choline and decreased proportionally to choline concentrati ons (0-10 mu M). For example, after 30 min of stimulation with K+ (25 mM), release in the absence of extracellular choline was similar to 25% of that associated with 10 mM choline. The vesicular transport blocker vesamicol (0 -5 mu M) almost completely prevented stimulated and basal ACh release at th e highest concentration evaluated, which suggests a mostly vesicular mode o f release in this model. The M-2-like muscarinic receptor antagonist AF-DX 384 (0-10 mu M) enhanced stimulated ACh release (similar to 150% at the hig hest concentration evaluated), whereas the nonspecific muscarinic receptor agonist oxotremorine (0-10 mu M) decreased stimulated release (similar to 6 0% at the highest concentration evaluated), suggesting that functional musc arinic autoreceptors exist in primary embryonic septal cultures. Novel find ings concerning ACh release from primary embryonic septal cultures are repo rted herein, and the demonstration of ACh release gives further credit to t he use of these cultures for studying cholinergic system functioning and in relation to physiology and pathology.