Do neurons have a reserve of sodium channels for the generation of action potentials? A study on acutely isolated CA1 neurons from the guinea-pig hippocampus
M. Madeja, Do neurons have a reserve of sodium channels for the generation of action potentials? A study on acutely isolated CA1 neurons from the guinea-pig hippocampus, EUR J NEURO, 12(1), 2000, pp. 1-7
The density of voltage-gated sodium channels is high in several regions of
the neuronal membrane. It is unclear if this density of channels represents
a reserve for the neuron, or if it fulfils a special role in action potent
ial firing. This problem was addressed by studying sodium currents and acti
on potentials in acutely isolated hippocampal CA1 neurons whose number of a
ctive sodium channels was acutely changed by applying the sodium channel bl
ocker tetrodotoxin (TTX) at different concentrations. The results show that
more than a third of the sodium channels can fail without affecting the si
ngle action potential. Thus, the neurons have a remarkable surplus of sodiu
m channels. The surplus, however, is necessary for repetitive action potent
ial firing, as every decrease in the fraction of sodium channels reduces th
e maximal frequency of action potentials that can be generated by the neuro
n.