CULTURED POSTNATAL RAT MEDIAL SEPTAL NEURONS RESPOND TO ACUTE ETHANOLTREATMENT AND NERVE GROWTH-FACTOR BY CHANGING INTRACELLULAR CALCIUM LEVELS

Ethanol neurotoxicity results in the loss of neurons during the develo pment of the nervous system. Nerve growth factor (NGF) can ameliorate the neurotoxic effects of ethanol (EtOH) in rat medial septal (MS) neu rons. These experiments study the effects of EtOH and NGF on neuronal calcium (Ca2+) homeostasis in cultured postnatal day of birth (PO) rat MS neurons. Previously, we observed that ROH and NGF modulate intrace llular Ca2+ levels ([Ca2+]i) in unstimulated and high potassium stimul ated (30 mM KCl) cultured rat embryonic day 21 (E21) MS neurons (Webb et al., Brain Res 701:61-74, 1995). The purpose of the present study w as to explore whether the effects of EtOH and NGF on Ca2+ homeostasis were altered by developmental stage. The hypotheses tested were the fo llowing: treatment with EtOH affects Ca2+ homeostasis in postnatal day of birth (PO) rat MS neurons by causing transient and persistent chan ges in [Ca2+]i; NGF modulates Ca2+ homeostasis in MS neurons by regula ting [Ca2+]i; the action of NGF changes the response of MS neurons to EtOH, thus altering Ca2+ homeostasis; and that EtOH and/or NGF effects on Ca2+ homeostasis are developmentally regulated. Our results indica ted that behaviorally relevant levels of EtOH caused a rapid transient increase in basal [Ca2+]i, whereas there was no effect of NGF on basa l [Ca2+]i. Ethanol and NGF interacted, resulting in the lowering of [C a2+]i. During stimulation with high K+, EtOH inhibited the change in [ Ca2+]i. NGF partially ameliorated this effect of higher levels of EtOH , allowing [Ca2+]i to increase. NGF and the lowest level of EtOH poten tiated the high K+ stimulated increase in [Ca2+]i. Ethanol and NGF eff ects on [Ca2+]i were different in the PO neurons compared with our pre viously published observations in E21 neurons, Therefore, these data s uggest that EtOH neurotoxicity and NGF protection involve mechanisms t hat regulate neuronal Ca2+ homeostasis, and the magnitude of these eff ects depend on developmental stage.