Mechanically insensitive afferents (MIAs) in cutaneous nerves of monkey

Richard A. Meyer, Karen D. Davis, Richard H. Cohen, Rolf Detlef Treede, James N. Campbell

Research output: Contribution to journalArticlepeer-review

Abstract

A problem in the study of nociceptors is that intense stimuli are used to locate the receptive field (RF), and thus the receptor may be damaged before the first responses are recorded. In addition, some nociceptors do not respond to the mechanical stimuli often used to search for the RF. To overcome these problems, an electrical search technique was developed to locate the RF of cutaneous nociceptors. In the hairy skin of anesthetized monkey, we used this technique to locate the RF of 63 Aδ-fibers and 22 C-fibers that had extremely high thresholds or were unresponsive to mechanical stimuli. We refer to these afferents as mechanically insensitive afferents (MIAs). Ten Aδ-fiber MIAs had a short latency response to stepped heat stimuli and could be responsible for first pain sensation. Five Aδ-fiber MIAs and one C-fiber MIA did not respond to mechanical or heat stimuli but did respond to injection into the electrical RF of an artificial inflammatory soup containing histamine, bradykinin, prostaglandin E1, and serotonin. These chemoreceptors might be responsible for the pain and itch sensations that result from chemical stimuli. Some MIAs became more responsive to mechanical stimuli after injection into the RF of the inflammatory soup and, thus, may contribute to the hyperalgesia to mechanical stimuli associated with cutaneous injury. A large proportion of the Aδ-fiber (48%) and C-fiber (30%) afferents in this study were insensitive to mechanical stimuli. The role of these MIAs in sensation needs to be studied further. The electrical search technique enables a systematic study of these afferents to be performed. This technique may also be of use to identify and characterize dorsal horn neurons that have inputs from MIAs.

Original languageEnglish (US)
Pages (from-to)252-261
Number of pages10
JournalBrain research
Volume561
Issue number2
DOIs
StatePublished - Oct 11 1991

Keywords

  • A-Fiber
  • C-Fiber
  • Chemoreceptor
  • Conduction velocity
  • Flare
  • Hyperalgesia
  • Inflammation
  • Itch
  • Nociceptor
  • Pain
  • Sensitization

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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