Qy. Liu et al., ASTROCYTES REGULATE AMINO-ACID RECEPTOR CURRENT DENSITIES IN EMBRYONIC RAT HIPPOCAMPAL-NEURONS, Journal of neurobiology, 33(6), 1997, pp. 848-864
Embryonic rat hippocampal neurons were cultured in a serum-fre e defin
ed medium (MEM/N3) either directly on poly-D-lysine (PDL) or on a conf
luent monolayer of postnatal cortical astrocytes, C6 glioma cells, or
Rat2 fibroblasts. Neurons on PDL were grown in MEM/N3 or in MEM/N3 con
ditioned for 24 h by astrocytes or C6 cells. Membrane capacitance (C-m
) and gamma-aminobutyric acid (GABA)-, glycine-, kainate-, and N-methy
l-D-aspartate (NMDA)-induced currents were quantified using whole-cell
patch-clamp recordings. C-m as well as the amplitude and the density
of these currents in neurons cultured on astrocytes were significantly
greater than those in neurons grown on PDL after 24 and 48 h. C6 cell
s mimicked astrocytes in promoting C-m and GABA-, glycine-, and NMDA-e
voked, but not kainate-evoked, currents. C-m and currents in neurons g
rown on Rat2 cells were comparable to those in neurons on PDL. Astrocy
tes maintained in culture for 3 months were noticeably less effective
than freshly prepared ones just grown to confluence. Suppression of sp
ontaneous cytoplasmic Ca2+ (Ca-c(2+)) elevations in astrocytes by 1,2-
bis(2-aminophenoxy) ehane-N, N, N, N-tetraacetic acid acetoxymethyl es
ter (BAPTA-AM) loaded intracellularly blocked the observed modulatory
effects. Medium conditioned by either astrocytes or C6 cells mimicked
the effects of direct coculture of neurons on these cells in promoting
C-m and amino acid-evoked currents. Inclusion of antagonists at GABA
and glutamate receptors in coculture experiments blocked the observed
effects. Thus, diffusible substances synthesized and/or secreted by as
trocytes in a Ca-c(2+)-dependent manner can regulate neuronal growth a
nd aminoacid receptor function, and these effects may involve neuronal
GABA and glutamate receptors. (C) 1997 John Wiley & Sons, Inc.