Resting discharge patterns of macular primary afferents in otoconia-deficient mice

T. A. Jones, S. M. Jones, L. F. Hoffman

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Vestibular primary afferents in the normal mammal are spontaneously active. The consensus hypothesis states that such discharge patterns are independent of stimulation and depend instead on excitation by vestibular hair cells due to background release of synaptic neurotransmitter. In the case of otoconial sensory receptors, it is difficult to test the independence of resting discharge from natural tonic stimulation by gravity. We examined this question by studying discharge patterns of single vestibular primary afferent neurons in the absence of gravity stimulation using two mutant strains of mice that lack otoconia (OTO-; head tilt, het-Nox3, and tilted, tlt-Otop1). Our findings demonstrated that macular primary afferent neurons exhibit robust resting discharge activity in OTO- mice. Spike interval coefficient of variation (CV=SD/mean spike interval) values reflected both regular and irregular discharge patterns in OTO- mice, and the range of values for rate-normalized CV was similar to mice and other mammals with intact otoconia although there were proportionately fewer irregular fibers. Mean discharge rates were slightly higher in otoconia-deficient strains even after accounting for proportionately fewer irregular fibers [OTO-=75.4±31.1(113) vs OTO+=68.1±28.5(143) in sp/s]. These results confirm the hypothesis that resting activity in macular primary afferents occurs in the absence of ambient stimulation. The robust discharge rates are interesting in that they may reflect the presence of a functionally 'up-regulated' tonic excitatory process in the absence of natural sensory stimulation.

Original languageEnglish (US)
Pages (from-to)490-505
Number of pages16
JournalJARO - Journal of the Association for Research in Otolaryngology
Issue number4
StatePublished - Dec 2008
Externally publishedYes


  • Discharge patterns
  • Gravity receptors
  • Primary afferents of the macula
  • Resting activity
  • Sensory deprivation
  • Spontaneous activity
  • Vestibular ganglion cells
  • Vestibular macula
  • Vestibular spontaneous activity

ASJC Scopus subject areas

  • Otorhinolaryngology
  • Sensory Systems


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