Bimodal effects of acetylcholine on synchronized calcium oscillation in rat cultured cortical neurons

To understand the plastic changes in neural network dynamics, we analyzed t he modulating effects of cholinergic agonists on synchronized Ca2+ oscillat ion in the rat primary cultured cortical neurons. At 5-10 days after establ ishment of the culture, neurons exhibited synchronized Ca2+ oscillation. Th is Ca2+ oscillation was derived from glutamatergic and gamma-aminobutyric a cid (GABA)ergic synaptic inputs from neighboring neurons. Application of ac etylcholine and nicotine increased, decreased, or did not change the freque ncy of synchronized Ca2+ oscillation, depending on the colonies in the cult ure, The presence of cholinergic neurons in the culture was confirmed by im munocytochemical staining. Our study provided evidence for the first time t hat cholinergic neurons exert excitatory influences on GABAergic neurons as well as glutamtergic neurons, resulting in bimodal effects on the frequenc y of synchronized Ca2+ oscillation in the cortical neural network. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.