TY - JOUR
T1 - Cation permeability change caused by l-glutamate in cultured rat hippocampal neurons
AU - Ozawa, Seiji
AU - Nakamura, Tomoko
AU - Yuzaki, Michisuke
N1 - Funding Information:
We thank Dr. Olav Sand for useful comments on the manuscript. We are also grateful to Mrs. Tomo Wada and Miss Tomoe Shinozaki for technical assistance. This research was supported by grants from the Ministry of Education, Science and Culture of Japan.
PY - 1988/3/8
Y1 - 1988/3/8
N2 - The ionic mechanism of the membrane permeability changes caused by l-glutamate in hippocampal neurons prepared from 17- to 19-day-old fetal rat in dispersed cell cultures was studied with the whole-cell variation of the patch electrode voltage-clamp technique. The cultured hippocampal neurons became sensitive to glutamate 7 days after plating, and thereafter the sensitivity gradually increased. The conductance increase caused by glutamate was voltage-sensitive, decreasing with membrane hyperpolarization at potentials more negative than -40 mV. The relative permeability of glutamate-activated channels to alkali metal and alkaline earth cations was estimated by reversal potential measurements. The alkali metal cations, Li+, Na+, K+, Rb+ and Cs+ were permeant to the glutamate channels, and the selectively among them was weak. The alkaline earth cations, Ca2+, Sr2+ and Ba2+ were more permeant than the alkali metals. The permeability ratios of these divalent cations relative to Na+ were 2.4 (Ca2+), 2.4 (Sr2+) and 2.8 (Ba2+), respectively. Mg2+ was much less permeant and the permeability ratio (PMg/PNa) was only 0.1. Anion conductance made no contribution to the glutamate-induced current. Functional implications of the glutamate-induced increase in Ca2+-influx were discussed.
AB - The ionic mechanism of the membrane permeability changes caused by l-glutamate in hippocampal neurons prepared from 17- to 19-day-old fetal rat in dispersed cell cultures was studied with the whole-cell variation of the patch electrode voltage-clamp technique. The cultured hippocampal neurons became sensitive to glutamate 7 days after plating, and thereafter the sensitivity gradually increased. The conductance increase caused by glutamate was voltage-sensitive, decreasing with membrane hyperpolarization at potentials more negative than -40 mV. The relative permeability of glutamate-activated channels to alkali metal and alkaline earth cations was estimated by reversal potential measurements. The alkali metal cations, Li+, Na+, K+, Rb+ and Cs+ were permeant to the glutamate channels, and the selectively among them was weak. The alkaline earth cations, Ca2+, Sr2+ and Ba2+ were more permeant than the alkali metals. The permeability ratios of these divalent cations relative to Na+ were 2.4 (Ca2+), 2.4 (Sr2+) and 2.8 (Ba2+), respectively. Mg2+ was much less permeant and the permeability ratio (PMg/PNa) was only 0.1. Anion conductance made no contribution to the glutamate-induced current. Functional implications of the glutamate-induced increase in Ca2+-influx were discussed.
KW - Alkali metal cation
KW - Calcium
KW - Cultured hippocampal neuron
KW - Magnesium
KW - Membrane permeability
KW - Whole-cell voltage-clamp
KW - l-Glutamate
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U2 - 10.1016/0006-8993(88)91601-0
DO - 10.1016/0006-8993(88)91601-0
M3 - Article
C2 - 2896060
AN - SCOPUS:0023845133
SN - 0006-8993
VL - 443
SP - 85
EP - 94
JO - Molecular Brain Research
JF - Molecular Brain Research
IS - 1-2
ER -