Single-channel currents trigger action potentials in small cultured hippocampal neurons.

Spontaneous neuronal impulse activity appears toplay a key role in some neural processes, such as the normal establishment ofinterneuronal connections during development. In addition, spontaneous impulsesmay be essential for the functional operation of neuronal networks. Mechanismsof spontaneous non-pacemaker impulse generation are, however, not well known. Inthis work, spontaneous electrical activity in small cultured hippocampal neuronsfrom rat was studied with tight-seal recording techniques. The resultsdemonstrate that spontaneous individual openings of single ion channels cantrigger impulse generation in these high-resistance cells. First, impulsesrecorded in the whole-cell mode were apparently induced by spontaneousplateau-potential events showing the characteristics expected from individualopenings and closures of ion channels. Second, patch-clamp recordings in thecell-attached configuration showed that openings of single ion channels in thepatch membrane could trigger cellular impulses, detected as biphasic currentdeflections. These findings suggest that the random gating of ion channelmolecules can be used as a mechanism for stochastic triggering of spontaneousimpulses in mammalian central neurons.