Astrocyte-conditioned saline supports embryonic rat hippocampal neuron differentiation in short-term cultures

Embryonic rat hippocampal neurons were cultured for 1-2 days in serum-free, HERES-buffered Tyrode's solution. The effects of cortical astrocytes and a strocyte-conditioned saline on neuron survival, membrane surface area and t he expression of functional amino acid neurotransmitter receptors were stud ied. Neurons grown in Tyrode's solution alone survived well for 1 day but d eteriorated thereafter both in terms of percent neurons surviving and the a mplitudes and densities of GABA-, glycine-, kainate- and NMDA-induced curre nts. Neurons grown in Tyrode's previously conditioned by astrocytes for 24 h had significantly larger apparent plasma membrane surface area, as indexe d by whole-cell membrane capacitance, and larger amplitudes and densities o f the amino acid-induced currents after both 1 and 2 days. The survival rat e and neurite outgrowth were also greater in the astrocyte-conditioned sali ne group after 2 days in culture. Similarly, neurons cultured on glass cove r-slips facing a confluent monolayer of astrocyte were larger in apparent p lasma membrane area and amino acid-induced currents than neurons cultured i n Tyrode's alone. Neurons cultured in saline conditioned by astrocytes prov ide a strategy to study the physiological basis of astrocyte-directed neuro nal differentiation in the absence of ambiguities arising from the inclusio n of sera and other additives often used in vitro. (C) 1998 Elsevier Scienc e B.V. All rights reserved.