Fractions enriched in pinched‐off nerve terminals and astrocytic glial cells were used to analyse the permeability of Ca++of the two membranes. Three experimental models were used to illustrate a principle difference of the excitatory versus the non‐excitatory cell membrane, with respect to Ca‐permeability. The effect of an increased [Ca++] on 86Rb+and 3H‐GABA transport was measured in medium containing low and high [K+]. The possibility of GABA stimulation of release of preaccumulated 45Ca++with low and high [K+] was compared in neurons and glia. Finally, the effect of depolarizing [K+] on the transmembranal Ca++‐gradient was measured by comparing the efficacy of the Ca‐ionophore A23187 to depolarize or to inhibit the 3H‐GABA uptake at these different [K+]. The data essentially confirms the picture of a potential dependent Ca++‐permeability in the neuron, while the permeability of the glial cells seems a “true” constant. It might be relevant to suggest the astrocyte a role as a “Ca‐buffer” with possibilities to control extracellular Ca++in cases of hyperactivity, this in analogy with what has been suggested for K+.
|Original language||English (US)|
|Number of pages||6|
|Journal||Acta Physiologica Scandinavica|
|State||Published - Jan 1 1981|
- glial cells
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