Cultured postnatal rat medial septal neurons respond to acute ethanol treatment and nerve growth factor by changing intracellular calcium levels

Abstract

Ethanol neurotoxicity results in the loss of neurons during the development of the nervous system. Nerve growth factor (NGF) can ameliorate the neurotoxic effects of ethanol (EtOH) in rat medial septal (MS) neurons. 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 EtOH and NGF modulate intracellular Ca2+ levels [Ca2+]i) in unstimulated and high potassium stimulated (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 was to explore whether the effects of EtOH and NGF on Ca2+ homeostasis were altered by developmental stage. The hypotheses tested were the following: treatment with EtOH affects Ca2+ homeostasis in postnatal day of birth (PO) rat MS neurons by causing transient and persistent changes in [Ca2+]i; NGF modulates Ca2+ homeostasis in MS neurons by regulating [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 indicated that behaviorally relevant levels of EtOH caused a rapid transient increase in basal [Ca2+]i, whereas there was no effect of NGF on basal [Ca2+]i. Ethanol and NGF interacted, resulting in the lowering of [Ca2+]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 potentiated the high K+ stimulated increase in [Ca2+]i. Ethanol and NGF effects on [Ca2+]i were different in the PO neurons compared with our previously published observations in E21 neurons. Therefore, these data suggest that EtOH neurotoxicity and NGF protection involve mechanisms that regulate neuronal Ca2+ homeostasis, and the magnitude of these effects depend on developmental stage.