Multiple sites of action potential initiation increase neuronal firing rate

Stephen A. Baccus, Christie L. Sahley, Kenneth J Muller

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Sensory input to an individual interneuron or motoneuron typically evokes activity at a single site, the initial segment, so that firing rate reflects the balance of excitation and inhibition there. In a network of cells that are electrically coupled, a sensory input produced by appropriate, localized stimulation can cause impulses to be initiated in several places. An example in the leech is the chain of S cells, which are critical for sensitization of reflex responses to mechanosensory stimulation. S cells, one per segment, form an electrically coupled chain extending the entire length of the CNS. Each S cell receives input from mechanosensory neurons in that segment. Because impulses can arise in any S cell and can reliably propagate throughout the chain, all the S cells behave like a single neuron with multiple initiation sites. In the present experiments, well-defined stimuli applied to a small area of skin evoked mechanosensory action potentials that propagated centrally to several segments, producing S cell impulses in those segments. Following pressure to the skin, impulses arose first in the S cell of the same segment as the stimulus, followed by impulses in S cells in other segments. Often four or five separate initiation sites were observed. This timing of impulse initiation played an important role in increasing the frequency of firing. Impulses arising at different sites did not usually collide but added to the total firing rate of the chain. A computational model is presented to illustrate how mechanosensory neurons distribute the effects of a single sensory stimulus into spatially and temporally separated synaptic input. The model predicts that changes in impulse propagation in mechanosensory neurons can alter S cell frequency of firing by changing the number of initiation sites.

Original languageEnglish
Pages (from-to)1226-1236
Number of pages11
JournalJournal of Neurophysiology
Volume86
Issue number3
StatePublished - Sep 26 2001

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Action Potentials
Neurons
Leeches
Skin
Motor Neurons
Interneurons
Reflex
Pressure

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

Cite this

Multiple sites of action potential initiation increase neuronal firing rate. / Baccus, Stephen A.; Sahley, Christie L.; Muller, Kenneth J.

In: Journal of Neurophysiology, Vol. 86, No. 3, 26.09.2001, p. 1226-1236.

Research output: Contribution to journalArticle

Baccus, Stephen A. ; Sahley, Christie L. ; Muller, Kenneth J. / Multiple sites of action potential initiation increase neuronal firing rate. In: Journal of Neurophysiology. 2001 ; Vol. 86, No. 3. pp. 1226-1236.
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