Vol. 292, Issue 2, 692-697, February 2000

Pharmacological Characterization of Endogenous Acetylcholine Release from Primary Septal Cultures

Daniel S. Auld , Jamie C. Day, Françoise Mennicken and Rémi Quirion

Douglas Hospital Research Centre (D.S.A., J.C.D., F.M., R.Q.), Departments of Neurology and Neurosurgery (D.S.A., R.Q.), Pharmacology and Therapeutics (R.Q.), and Psychiatry (R.Q.), Faculty of Medicine, McGill University, Montreal, Quebec, Canada.

A detailed investigation of endogenous acetylcholine (ACh) release from primary embryonic septal cultures is described in this study. Applications of veratridine (25 µM) or increasing extracellular concentrations of K⁺ (6-100 mM) induced robust increases of endogenous ACh release (~500-15,000 fmol/well/10 min). Release stimulated with K⁺ (25 mM) was sustainable and did not differ significantly over 180 min. ACh release was dependent on extracellular choline and decreased proportionally to choline concentrations (0-10 µM). For example, after 30 min of stimulation with K⁺ (25 mM), release in the absence of extracellular choline was ~25% of that associated with 10 µM choline. The vesicular transport blocker vesamicol (0-5 µM) almost completely prevented stimulated and basal ACh release at the highest concentration evaluated, which suggests a mostly vesicular mode of release in this model. The M₂-like muscarinic receptor antagonist AF-DX 384 (0-10 µM) enhanced stimulated ACh release (~150% at the highest concentration evaluated), whereas the nonspecific muscarinic receptor agonist oxotremorine (0-10 µM) decreased stimulated release (~60% at the highest concentration evaluated), suggesting that functional muscarinic autoreceptors exist in primary embryonic septal cultures. Novel findings concerning ACh release from primary embryonic septal cultures are reported herein, and the demonstration of ACh release gives further credit to the use of these cultures for studying cholinergic system functioning and in relation to physiology and pathology.