ELEVATED POTASSIUM ENHANCES GLUTAMATE VULNERABILITY OF DOPAMINERGIC-NEURONS DEVELOPING IN MESENCEPHALIC CELL-CULTURES

This study examines the effects of high K+ concentration on the growth and development of mesencephalic cells and their glutamate vulnerabil ity. Mesencephalic cell cultures obtained from Wistar rat embryos on t he 14th gestational day were maintained for 14 days in medium with eit her normal (4.2 mM) or elevated (24.2 mM) potassium concentration. The re was no significant difference due to various K+ concentration in ce ll growth and survival up to day in vitro (DIV) 13-15. In order to tes t the glutamate (Glu) vulnerability, cultures were treated with 100 mu M Glu for 15 min in salt solution on the DIV 3, 6, 8, and 13. Glu-ind uced neuronal damage was estimated 24 h later by measuring the neuron- specific enolase (NSE) content in the culture medium and by counting t he number of tyrosine hydroxylase-immunoreactive (TH-IR) neurons. Glu had no damaging effect on the cells on DIV 3, but became pronounced be yond DIV 6. Elevated potassium concentration (24.2 mM) in the culture medium during development significantly increases neuronal vulnerabili ty to Glu treatment, indicated by a higher increase of NSE content in the medium and by a more pronounced Glu-induced decrease of the number of TH-IR cells. The Glu-induced decrease of the number of TH-IR cells and of NSE-IR cells let us conclude that dopaminergic neurons are mor e vulnerable to glutamate than other neurons from mesencephalic cultur e. (C) 1996 Academic Press, Inc.