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. 1972 Sep;225(2):363–390. doi: 10.1113/jphysiol.1972.sp009945

Injections of calcium ions into spinal motoneurones

K Krnjević, A Lisiewicz
PMCID: PMC1331111  PMID: 5074394

Abstract

1. In cats under Dial anaesthesia, Ca2+ was injected inside lumbosacral motoneurones, by passing currents between CaCl2- and KCl-containing barrels of compound micropipettes.

2. There was a reduction in excitability and a fall in membrane resistance, both rapid in onset and quickly reversible.

3. The minimum effective injection current was ≈ 10 nA, and the effect reached a maximum with currents of ≈ 30 nA. The mean slope of resistance change against injection current was -1·7%/nA (S.E. 0·35).

4. The most common change in membrane potential was a hyperpolarization; but in nearly half the cases, there was no clear change or a small depolarization. A reversal level for the effect of Ca2+ could be measured in five cells: on the average, it was 10 mV more negative than the resting potential.

5. Observations on i.p.s.p.s showed that Ca2+ probably does not alter gCl: it was concluded that the fall in membrane resistance caused by intracellular Ca2+ is mainly due to an increase in gK.

6. These results confirm previous suggestions that a steep transmembrane gradient of Ca2+ is essential for the maintenance of a low membrane conductivity, and that a rise in internal free Ca2+ — whether due to influx or release from internal stores — may play an important role in regulating neuronal activity.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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