Patterns of innervation of outer hair cells in a chimpanzee: I. Afferent and reciprocal synapses

Howard W. Francis, Joseph B. Nadol

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Three varieties of synaptic specialization, afferent, efferent, and reciprocal, have been demonstrated at the base of outer hair cells of one chimpanzee. The purpose of the present study was to investigate the innervation density of afferent and reciprocal synapses in the three rows and three turns of the organ of Corti. The data presented is based on light and electron microscopy from one aged chimpanzee using serial section electron microscopy. Afferent fibers make contact with outer hair cells as either terminal swellings or en passant contacts. In addition to membrane specialization, presynaptic bodles were present at the majority of afferent synapses. The mean innervation density of afferent endings was highest in the middle turn. Reciprocal endings were found on 74% of all outer hair cells. The average number of reciprocal endings increased from the base to apex and, except in the apical turn, from the first to third row of outer hair cells. On the basis of morphological criteria, endings with a reciprocal synapses were more similar to afferent than to efferent endings.

Original languageEnglish (US)
Pages (from-to)184-190
Number of pages7
JournalHearing Research
Issue number2
StatePublished - 1993
Externally publishedYes


  • Afferent innervation
  • Organ of Corti
  • Outer hair cell

ASJC Scopus subject areas

  • Sensory Systems


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